Principles are ways of successfully dealing with reality to get what you want out of life.
Ray Dalio, one of the world’s most successful investors and entrepreneurs, cites principles as his key to success.
Take passion, for example. Without passion, life would be dull; you wouldn't want to live without it. But what's key is what you do with your passion. Do you let it consume you and drive you to irrational acts, or do you harness it to motivate and drive you while you pursue your real goals? What will ultimately fulfill you are things that feel right at both levels, as both desires and goals.