I decided to be honest with myself about what I do and do not like, to work my ass off at the things I do like, and to be vigilant about checking my feelings and following my gut. It's paid enormous dividends. I taught myself to program and have gotten good jobs because of it, and I've also avoided going down a lot of blind alleys. I quit academia after completing a Master's rather than chase a PhD I didn't really want and saved myself enormous heartache there. Several times I've started developing skills only to realize, "I hate doing this." So I just stopped. I left numerous jobs where I was unhappy for various reasons and have stayed at one where so far I've been happy. And overall this attitude has kept me growing and pretty happy in my career and life generally.

EDIT: As a part of this: I was honest with myself that I cared about money (to a point). For a while I stayed in a job I liked that didn't pay me well, trying to convince myself that "quality of life" was more important than money. The reality for me is that money is part of the quality of life equation, and I'm glad I admitted that to myself. It was also sort of a canary that I wasn't being challenged and could do tougher work that paid better.