I like the philosophy expressed by the OP.
I'm less of a fan of "be careful". When I was a kid that's one of the few things that my parents could say that I'd completely ignore. The risks I didn't take were simply the ones I was afraid to take. I may be wrong, but I think this is probably true of most kids, they are as careful as their own innate fears make them.
Making them aware of dangers that they may have overlooked might be useful though.
This is what "be careful" means, that you take into account only what you are afraid, your parents cannot be careful for you.
Out of the things that you parents tell you, you will consider only the things that make sense. If your parents telling you things which don't make sense, well they don't make sense to you and you don't do them.
Making sense of things at any time happens with avoiding risks, which you are afraid to take at the time, and taking risks, which you are not afraid to take at the time. For the latter, when you take risks and fail, you learn to be afraid of doing exactly the same thing as you did.
ETA: Here's a little anecdote from my childhood about "be careful". When I was six I wanted to go play outside. As I was running out the door my mother told me to put on shoes, but I refused. We argued for a bit, but I eventually promised to be careful, and she let me go out barefoot.
So, I walked down the path behind our house and turned left at the street. There I found a broken beer bottle. This looked like fun! I jumped over it. Great thrill! I jumped over it again. The thrills just kept coming with every leap. My younger sister showed up, and saw what I was doing and told me that I was crazy and to stop. I told her that it was fine, I was good at jumping. Then I landed on the broken glass. My sister started crying and ran home screaming. I hopped home with a nice trail of blood behind me. Happily while there was a lot of blood no serious harm accrued and my foot healed up fine. At no point did my promise to be careful even cross my mind. I didn't feel that I was blatantly breaking that promise. I felt that I was being careful.
you were careful, apparently getting cut with broken glass doesn't bother you.
You didn't mention in your message, how your mother reacted and what happened in the future? Did you continue to jump on broken glass, if yes, do you still do it?
If you do, how many other people want to step on broken glass with you to have fun together?
If you don't, why did you stop, you said it was thrilling for you, why isn't it thrilling now?
And the reason why I am asking these questions, is that humans built common sense when they use their senses commonly, so that they don't harm others or themselves. And on the latter, finding out what harms you or not, you will need to try something first, unless you are afraid of the risk involved, in which case you avoid it.