Avoid all evil, cultivate all good and purify one's mind

This is the teaching of all the Buddhas. When you live your life striving this you will gain true wisdom about life. It's essentially how karma works. When you act with a clouded mind you don't always get the results you wanted. But when you pay attention to everything you think, say and do and do this with the best intention for yourself and others, you will get great results.