"Normals" have ups and downs too. Where it becomes a problem is when you can't get out of the low spot. Remember recovery is not necessarily feeling great, it's more about finding a level you're comfortable with. Don't know if you're on meds, but some of us need them to feel less depression. I am not a pusher or think they are for everyone but some us couldn't survive without them.

As for causes of depression, there are many factors. In my case I was either born this way or a childhood head injury or just a crappy life growing up.

I hope you find what will help you improve your life. Most of all be patient with yourself and don't let lack of progress get you down.