Depression is an illness and I suffer it. I do agree that the environment or my circumstances can determine how I feel. The one thing that illnesses have in common is that there are good days at times. There are days that it seems like an illness is all over with. But it comes back.

With me there can be a stretch when my depression seems like it just disappeared. It's a nice feeling when that happens. But in time it can come back.

I suffer from SAD, and I tend to get very depressed starting in the early spring and it goes into summer. From fall to early spring, my depression either eases or goes away, except for the holiday season.