I had two good careers, but that doesn't make me happy since both of them are done. I wanted a third one...like a park ranger or a pimp, but I don't have the energy.
Most people that I know, including me, who were happy in their jobs, were not in the jobs they originally dreamed of having. I believe it's important to pay attention to what about your job makes you happy and then keep moving in that direction.
I have a rewarding job.
I try pretty hard to be happy and positive every day. I'm fairly successful most days.
(I have 2 youngish, healthy dogs. That helps a LOT!)