Realize benefit from your ability to see the good and think only in a positive way. First, it is to improve your health, because if you will not survive the stress, you will improve hormonal balance, which, in turn, depends on the work of many organs and systems in the body. Secondly, your good mood will be like a magnet to attract to you good people. Thirdly, you have to triple the force to carry different loads. And finally, you will be able to achieve many goals, because you will gain confidence in their abilities and capabilities.
First of all, try to keep yourself from negative emotions. And even if in your life and it was something out of the ordinary, do not dive for a long time in a stressful situation. Learn how negative thoughts translate from the realm of emotions in analytic.
For example, give yourself a few minutes to slightly "move" and start analyzing the situation using known psychological technique of three questions:

1. What good can you find in this situation?
2. What conclusions can we draw and what to learn?
3. How can I fix this situation based on the findings?

When you learn the negative to this behavior, your thoughts will acquire a different coloration.
If you react to an event negatively, try to mentally make three positive argument with the word "but". For example, "I'm late(a) on the bus, but received... (a) walk in the fresh air", etc.
Try to treat the people who are doing something absurd, not with annoyance, but with humor. Same thing with different situations. Find them something funny.
Note, for example, 10 days, during which you will try to think only positively. And whatever is going on, try to only see the positive side and think of what benefits you can extract from the situation. Not to notice the problem, you can not, but pay attention only to the ways of its solution.
Create for yourself a special notebook where before going to sleep write down everything good that happened and that you are pleased with. It should be at least 8-10 points. If at first you will fail, look, later you will remember such events with ease.
Try every day at least a little to do something good for people around you. You will see that the world around you has changed for the better.
To learn to see the good around you, try to see more good in yourself. Be honest with yourself, and not procrasinate its shortcomings. But instead of berating yourself for them, think about how you can correct them. And when something difficult to overcome, do not forget to put a "plus". Changing yourself for the better you differently and perceive the world around us.