I don't think I'd be in a very sound state of mind, being completely alone and having lost everyone I love. I think that the only thing worth doing at that point would be cleaning up and fixing as much as I can, to make as much of the world safe for post-human life as possible. By this I mean things like shutting off power grids so that everything will be safer for the remaining life. Between all remaining houses, cars, and stores, I should be able to sustain myself long enough to make at least a bit of a difference for the world before I'm gone.
If the world were destroyed too much, though, I don't think that there would be much of a point in me lingering around just to eventually die of exposure or starvation.