How can I overcome the fear that my depression makes me a bad parent?

I am in my 30s and married with two young children. Since adolescence I have had periods of depression and of feeling suicidal.

Throughout these times I’ve remained relatively functional – studied, worked in a very stressful job, and looked after myself. However, I always have this sense of just not knowing how to be happy. I’ve been on antidepressants several times and I see a therapist.