Positive thoughts are more important than you realize. Negative thinking provokes stress, anxiety, depression and many other related illnesses. It keeps people stuck in their misery and many times it's the cause of it. Negative thinkers think negatively out of habit! It may be a learned behavior from our parents or simply a habit we have grown towards simply because we've had too many negative events take place in our lives and not enough positive to counteract them.
It is very important to realize what you say to yourself on a daily basis. Your self talk matters more than you realize. Many of us are tuned into the thoughts in our heads and many of us are not. Some of those are positive thoughts and some of them are negative thoughts. It helps to journal our thoughts daily. By doing so, we are better able to spot our negative self-talk and it guides us into finding more positive thoughts to replace them with.
I have to be honest, this can be very difficult, especially if you are used to letting your brain chatter and chatter all day long with no control. Our brains think and think all day long. Even when we sleep our brains are still working. Our brains have no choice but to believe whatever we tell it. Therefore, people who are habitual negative thinkers usually feel the effects physically. The mind and body are so connected that they respond to each other. In other words, if you are telling yourself "I am tired, I can't do it , I am fearful" then you will feel the effects of this thinking in your body!
Learning how to use positive thoughts and affirmations properly takes time and patience! I recommended writing in a journal. Then by reading your journal you will be able to spot your negative thoughts more easily. Try to find positive thoughts that can be realistic replacements. Once you find them, write them down and repeat them to yourself over and over again, especially when you find yourself repeating those negative thoughts to yourself.