I once came across a quote that said, “If you have enthusiasm you don’t need happiness.” I wish I could find it again to give proper accreditation.
What is happiness in neurological terms? Dan Gilbert, a harvard psychologist and researcher, says that in normal human beings, no matter the circumstance, it returns. We are all blessed, and cursed, with a kind of psychological immune system. Whether we are happy or sad today, even in the extreme, it is likely that we will return to our normalized state within a short period of time.
See Gilbert’s TED talk.