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.
The answer doesn't have to be in your head; you can look outside yourself. If you're truly looking at things objectively, you must recognize that the probability of you always having the best answer is small and that, even if you have it, you can't be confident that you do before others test you. So it is invaluable to know what you don't know. Ask yourself: Am I seeing this just through my own eyes? If so, then you should know that you're terribly handicapped.