While growing up you are trying to figure out how things work and you build the rules according to your experiences. There is in general nothing wrong with this as it works in a lot of cases. You learn that glass bursts when it falls down onto the tiles, you learn that 2+2 is 4 and so on.
We feel more secure and it makes our decisions easier when we have rules. However, often we could get a better outcome if we do not only have rules but also have principles and pay more attention to principles than on rules in cases we are not sure about the next step. More - it can be better to completely prefer to focus on principles over rules. World is very complex and so your rules can also become very complex and you could easily loose the overview and further you get inflexible.
This summer I read an article (How to Renew Yourself as a Leader - Part 1) that shows a very good example where principles are more important than rules: If you are leading a large teams than you can't have the overview what happens at lower - more concrete - levels. You have to rely on the team members in their ability to proper valuate and decide what to do. So you have to rely on their intelligence to realize the big picture.
Defining principles and goals is more important than defining rules.
Although rules do not necessarily have to be very concrete they have an inflexible character. You would also label the word "goal" with the attribute "fixed" - however the way how you achieve the goal is free. Principles are more a direction - a helping hand when it comes to decisions.
Related posts: Setting borderlines, Direction over goals, Focus by direction, Focus by decision, Finding the proper priorities, Between short and long term goals, The main purpose, Living your opportunities, The golden rule, Replace constraint with freedom, Considerations on decisions.