I became much happier when I realized I shouldn't depend solely on my career for my sense of self. So I developed other interests and surrounded myself with a small group of friends I could trust.
But so much of being an actor isn't so great - the auditioning, the rejection, the financial insecurity.
Originality is, for me, the most important quality in a script.
Fear of failure has always been my best motivator.
I know a lot of people in the business recommend the many Story Structure seminars being offered here, but I point to them as the single biggest contributor to lousy scripts.