I think we keep imagining a totally happy life with roses and sunshine. But let's not lose track of the fact that even "normal" people have bad days. Therefore to reach the point you call "normal" will still include those down days every now and again. I guess the difference is the duration of these down periods and the reasoning behind the depression.
I think we sometimes strive for too perfect a life, when we are possibly actually pretty stable.
And I definitely believe that the correct medication and treatment will go an awful long way to helping us out - how close to normal it can really bring us: I don't know

P.S.: Hope that didn't totally confuse everyone