Eventually, if they're unlucky (or lucky, I suppose), one might stumble into a rut deep enough that even without any influence of some ancient kung fu wisdom they come to the realization that love and happiness can only ever come from within. (Which is not the same as "self love")
We usually speak about "(not) letting something bad get to you" but nothing good from without can reach in either unless you let it.
Tldr
Rule 1. Don't be a cunt
Rule 2. If you're not, don't (over)think you are; if you are, refer to rule 1