I think you're right, Anvil, but I know I got HUGE self-esteem from my job. When I was temporarily unable to do it, when I moved away and was unable to find anything remotely as satisfying, I felt truly bereft. It was also a huge motivator for me to get sober--I don't know how I would have dealt with losing my job over my addiction.
A friend of mine, who has an important job but has run into a lot of administration-related headaches that have caused him a lot of personal strife, is fond of saying, "You may love your job, but it won't love you back." And he's probably right. But I think productive work--using our talents in the best way we can--is a legitimate source of self-esteem. Particularly where the job satisfaction is based on more than how much money you make or how much power you have. Those are less satisfying--for me, anyway.