I sometimes get calls for help from old friends, and have had a couple of those recently. Anxiety and depression. I don't know how to treat either anxiety or depression, beyond the usual prescriptions like prozac, so other than that I'm at a loss as to what to recommend to others beyond finding purpose(s) in your life.
I don't suffer from anything like depression, though I do occasionally have "down" moments. When those moments come the self-advice I try to take is in two parts. First, work at something difficult or unpleasant but necessary and important, even if it is as small as household chores or physical exercise. Second, if the weather permits, take a long drive out into the countryside (in my case usually to a reservoir) and listen to Zero-7 on the way. I think it's important that the work comes first, and play comes second; you've got to earn your happiness.