Quotes on Optimism from The Power of Positive Thinking by Norman Vincent Peale 

“A man who is self-reliant, positive, optimistic, and undertakes his work with the assurance of success magnetises his condition. He draws to himself the creative powers of the universe.” 

"If your eyes are looking down in the mud and you feel a sense of failure, you will create defeat for yourself. Optimistic visualisation combined with prayer and faith will inevitably actualise achievement." 

"It is indeed a fact that the person who thinks with positive self-reliance and optimism does magnetise his condition and releases power to attain his goal. So expect the best at all times." 

"A second method for drawing upon that Higher Power is to learn to take a positive, optimistic attitude towards every problem. In direct proportion to the intensity of the faith which you muster will you receive power to meet your situations. “According to your faith be it unto you,” (Matthew ix. 29.) is a basic law of successful living." 

"Mark every passage in the Bible that speaks of faith, hope, happiness, glory, radiance. Commit each to memory. Say them over and over again until these creative thoughts saturate your subconscious mind. Then the subconscious will return to you what you have given it, namely, optimism, not worry." 

"Dr. Karl Menninger said: “Attitudes are more important than facts.” That is worth repeating until its truth grips you. Any fact facing us, however difficult, even seemingly hopeless, is not so important as our attitude towards that fact. How you think about a fact may defeat you before you ever do anything about it. You may permit a fact to overwhelm you mentally before you start to deal with it actually. On the other hand, a confident and optimistic thought pattern can modify or overcome the fact altogether." 

Following are seven practical steps for changing your mental attitudes from negative to positive, for releasing creative new thoughts, and for shifting from error patterns to truth patterns. Try them—keep on trying them. They will work.

1. For the next twenty-four hours, deliberately speak hopefully about everything, about your job, about your health, about your future. Go out of your way to talk optimistically about everything. This will be difficult, for possibly it is your habit to talk pessimistically. From this negative habit you must restrain yourself even if it requires an act of will. 
2. After speaking hopefully for twenty-four hours, continue the practice for one week, then you can be permitted to be ‘realistic’ for a day or two. You will discover that what you meant by ‘realistic’ a week ago was actually pessimistic, but what you now mean by ‘realistic’ is something, entirely different; it is the dawning of the positive outlook. When most people say they are being ‘realistic’ they delude themselves: they are simply being negative. 
3. You must feed your mind even as you feed your body, and to make your mind healthy you must feed it nourishing, wholesome thoughts. Therefore, today start to shift your mind from negative to positive thinking. Start at the beginning of the New Testament and underscore every sentence about Faith. Continue doing this until you have marked every such passage in the four books, Matthew, Mark, Luke, and John. Particularly note Mark xi., verses 22, 23, 24. They will serve as samples of the verses you are to underscore and fix deeply in your consciousness. 
4. Then commit the underscored passages to memory. Commit one each day until you can recite the entire list from memory. This will take time, but remember you have consumed much more time becoming a negative thinker than this will require. Effort and time will be needed to unlearn your negative pattern. 
5. Make a list of your friends to determine who is the most positive thinker among them and deliberately cultivate his society. Do not abandon your negative friends, but get closer to those with a positive point of view for a while, until you have absorbed their spirit, then you can go back among your negative friends and give them your newly acquired thought pattern without taking on their negativism. 
6. Avoid argument, but whenever a negative attitude is expressed, counter with a positive and optimistic opinion. 
7. Pray a great deal and always let your prayer take the form of thanksgiving on the assumption that God is giving you great and wonderful things; for if you think He is, He surely is. God will not give you any greater blessing than you can believe in. He wants to give you great things...

How to Break the Worry Habit

1. Say to yourself: “Worry is just a very bad mental habit. And I can change any habit with God’s help.” 
2. You became a worrier by practicing worry. You can become free of worry by practising the opposite and stronger habit of faith. With all the strength and perseverance you can command, start practising faith. 
3. How do you practise faith? First thing every morning before you arise say out loud. ‘I believe’, three times. 
4. Pray, using this formula: ‘I place this day, my life, my loved ones, my work in the Lord’s hand. There is no harm in the Lord’s hands, only good. Whatever happens, whatever results, if I am in the Lord’s hands it is the Lord’s will and it is good.’ 
5. Practise saying something positive concerning everything about which you have been talking negatively. Talk positively. For example, don’t say: ‘This is going to be a terrible day’. Instead, affirm: ‘This is going to be a glorious day’. Don’t say: “I’ll never be able to do that.” Instead, affirm: ‘With God’s help I will do that’. 
6. Never participate in a worry conversation. Shoot an injection of faith into all your conversations. A group of people talking pessimistically can infect every person in the group with negativism. But by talking things up rather than down, you can drive off that depressing atmosphere and make everyone feel hopeful and happy. 
7. One reason you are a worrier is that your mind is literally saturated with apprehension thoughts, defeat thoughts, gloomy thoughts. To counteract, mark every passage in the Bible that speaks of faith, hope, happiness, glory, radiance. Commit each to memory. Say them over and over again until these creative thoughts saturate your subconscious mind. Then the subconscious will return to you what you have given it, namely, optimism, not worry. 
8. Cultivate friendships with hopeful people. Surround yourself with friends who think positive, faith-producing thoughts and who contribute to a creative atmosphere. This will keep you re-stimulated with faith attitudes. 
9. See how many people you can help to cure their own worry habit. In helping another to overcome worry you get greater power over it within yourself. 
10. Every day of your life conceive of yourself as living in partnership and companionship with Jesus Christ. If He actually walked by your side, would you be worried or afraid? Well, then, say to yourself: ‘He is with me’. Affirm aloud: ‘I am with you always’. Then change it to say: ‘He is with me now’. Repeat that affirmation three times every day. good.’

"Another effective technique in developing a peaceful mind is the daily practice of silence. Everyone should insist upon not less than a quarter of an hour of absolute quiet every twenty-four hours. Go alone into the quietest place available to you and sit or lie down for fifteen minutes and practise the art of silence. Do not talk to anyone. Do not write. Do not read. Think as little as possible. Throw your mind into neutral. Conceive of your mind as quiescent, inactive." 

Following are ten simple, workable rules for overcoming inadequacy attitudes and learning to practise faith. Thousands have used these rules, reporting successful results. Undertake this programme and you, too, will build up confidence in your powers. You, too, will have a new feeling of power.

1. Formulate and stamp indelibly on your mind a mental picture of yourself as succeeding. Hold this picture tenaciously. Never permit it to fade. Your mind will seek to develop this picture. Never think of yourself as failing; never doubt the reality of the mental image. That is most dangerous, for the mind always tries to complete what it pictures. So always picture ‘success’ no matter how badly things seem to be going at the moment. 
2. Whenever a negative thought concerning your personal powers comes to mind, deliberately voice a positive thought to cancel it out. 
3. Do not build up obstacles in your imagination. Depreciate every so-called obstacle. Minimise them. Difficulties must be studied and efficiently dealt with to be eliminated, but they must be seen for only what they are. They must not be inflated by fear thoughts. 
4. Do not be awe-struck by other people and try to copy them. Nobody can be you as efficiently as YOU can. Remember also that most people, despite their confident appearance and demeanour, are often as scared as you are and as doubtful of themselves. 
5. Ten times a day repeat these dynamic words, “If God be for us, who can be against us?” (Romans viii. 31.) (Stop reading and repeat them NOW slowly and confidently.) 
6. Get a competent counsellor to help you understand why you do what you do. Learn the origin of your inferiority and self-doubt feelings which often begin in childhood. Self-knowledge leads to a cure. 
7. Ten times each day practise the following affirmation, repeating it out loud if possible. “I can do all things through Christ which strengtheneth me.” (Philippians iv. 13.) Repeat those words NOW. That magic statement is the most powerful antidote on earth to inferiority thoughts. 
8. Make a true estimate of your own ability, then raise it 10 per cent. Do not become egotistical, but develop a wholesome self-respect. Believe in your own God-released powers. 
9. Put yourself in God’s hands. To do that simply state, “I am in God’s hands.” Then believe you are NOW receiving all the power you need. ‘Feel’ it flowing into you. Affirm that “the kingdom of God is within you” (Luke xvii. 21) in the form of adequate power to meet life’s demands. 
10. Remind yourself that God is with you and nothing can defeat you. Believe that you now RECEIVE power from Him.

"I certainly do not ignore or minimize the hardships and tragedies of the world, but neither do I allow them to dominate." 

Read more of these inspiring quotable quotes in "Optimism: The How and Why" by Victor Perton, CEO of The Centre for Optimism.

Project Optimism has produced "The Optimist's Gratitude Journal: 100 days to share and develop your gratitude" which is very helpful.

See https://www.amazon.com/Optimists-Gratitude-Journal-develop-gratitude/dp/B09MC5ZNPX