I was diagnosed with dysthymia last year. In the past doctors always assumed I was going through a major depressive episode and would put me on some SSRI which would either have nasty side effects or just not work. I have always been a melancholic person; my first depression diagnosis was in my teens. I do have times when I drop into a full depressive episode, which gradually works its way back up to my "slightly-below-happy" usual mood.
When I was diagnosed with dysthymia and put on mood stabilisers instead of anti-depressants I experienced a marked improvement in my condition.
Not that I'm unhappy or miserable - I consider myself as happy as the next person - my personality type is just not that of the happy-go-lucky, the incessantly cheerful or the optimist. I feel emotions very deeply and small things can really get me down and affect me for a while. Some days I just feel like sleeping all day or crying for no reason. Other days I'll make it through without a hitch. So dysthymia is a tricky thing: not easy to identify, and even trickier to manage, because sometimes the line between dysthymia and a major depressive episode can become quite blurred.