Principles are generalized rules that drive a situation to a successful outcome. E.g.: if you know that the first impression matters a lot in any relationship, you will do your best to get it right every time you meet someone new.
I believe Ray Dalio is a great thought leader on the matter of principles. In his book ‘Principles’ he has summarized his findings on the topic. He says that there are only 100-120 general situations in life that repeat time after time with a little difference. If you identify the core principles in each of them basically you have mastered your life.
What’s hard about it is that before acting, you have to stop (keep space between stimulus and response), figure out what is the win-win outcome for each party involved (begin with the end in mind), and identify the success principle. You can even do this through retrospective reflection.
The point is, you shouldn’t repeat your past mistakes and rely on your gut feelings on how to act.
What we refer to as “law” is basically a collection of principles, which were once recorded, to guide us about what’s right and what’s not in a given situation.
Know your principles and you will master your life.