A difficult question!
I feel I have no choice other than medicine.
Uh, this sounds silly, but there's really nothing else I find interesting enough for doing it every day, for 40-50 years (hopefully

I'm a senior medical student now)
I think that many physicians who are dissapointed in their job feel that way beacause they had unrealistic expectations about the emotional rewards of their job. They had dreams about solving difficult diagnostic and therapeutic problems, making changes in people's lives, grateful patients thanking for the efforts of their physician, beind admired by friends, family, neighbours etc
I have these dreams myself, but I try not to let my dreams become my expectations. Instead, I try to appreciate the small rewards of my job. In fact, I often feel job satisfaction when I get a simple "thank you" or when I understand an important fact while studiyng.
I hope I won't loose my enthusiasm for medicine because of the boring daily routine, angry patients, hopeless situations...
I wonder what my answer would be to this question in 20 years.
Anybody here who has been practicing medicine for 20 years? Do you still have your dreams??