It hasn't been diagnosed yet, but from one of my friends who has been diagnosed, I exhibit all the symptoms of depression and have for a couple of years now. It developed while I was in middle school, and steadily got worse. Since I met my girlfriend, though, it seems to have gotten better. People have told me they've noticed a difference in the way I act. Despite that, though, it still lingers in the back of my mind and strikes when I'm vulnerable.
As for words of encouragement, I would have to go with Andrew W.K. on this one. "Don't give up just because things aren't easy." Even if it seems like things are going horrible and that there's no end to what you're going through, there is. I, and many others, have made it through this, and things ALWAYS get better. Whatever you do, don't give up. The good is on it's way.