Perspective, BlueMoon878. Nobody feels good all the time, but us depressed people, oy gevalt, when we're down, we're really down. Most people know that their low moods are transitory, but no, we people with depression have ourselves convinced that it's the end of the world.
Here's what gets me through the lows. There are three things that are very important in my life: my wife, my job, and my friends. I know, at least in the case of the first two, that I make a difference. I hold in my mind that I have a definable purpose for the days/weeks/months/years it takes for me to start thinking right again. In other words, if my brain doesn't want me to exist just for me, I'll bridge that time by existing for someone else.
Remember, it's not the end of the world BlueMoon878, it just feels like it. ;-)