The depression may well be resurfacing because you're teetering on the edge of diving into something painful. My depressive troughs are often triggered by dread. If you dig in, at least you don't have to dread it anymore.

As far as eradicating depression, I have not had success with it. It cycles, and, unfortunately, and perhaps depressingly, each major depression you have in your life puts you at a greater risk for having another one. I have, however, had success with decreasing the depth and length of my depressions. Before I started therapy, I did not know what it felt like to not be depressed at all. That was just not part of my life experience. (I guess I could have been described as dysthymic with occasional terrible periods of nearly unbearable darkness) I have since experienced some time without depression, and it's pretty sweet. If you can recognize what's happening and use your resources the severity doesn't get quite so out of hand.