Why the dichotomy?

If a test regularly returns 'you have cancer' when I have cancer, and regularly returns 'you have cancer' when I don't have cancer, it's not a good test.

Similarly, if a principles guides people to be successful, and it guides people to be unsuccessful, it is not a good principle.

For example: it could be said that "eat food at least daily, drink water at least daily, and sleep daily or close to it" is a principle that hugely successful people follow. It is also a principle that not hugely successful people follow. Following this principle will not make me hugely successful.

I could just say "Pr(not successful | follows principle) needs to be low, otherwise base rate makes it meaningless".