The advice one friend gave me was to observe the tiny little things that give you pleasure. So small, uncomplicated -- like water droplets on a leaf, the fact that it feels really great to down a glass of water when you're thirsty, or just how fucking amazing the sunrise is when you get to catch it. And really savor it. Then think about why you like it. And it is a tiny thing, but it helped me to move through a period of serious negative / isolated / depressed energy (these are cyclic for me).
It's not the "gratitude lists" that Oprah talks about (which are good too), because when I'm isolated and negative those become too complicated, charged, and don't feel fully authentic. But realizing that I really do love how my warm comforter is sitting on my legs and why I love it (because it signals being happy and at home and relaxing and warm) is just a drop in the bucket that needs to get filled.
Also - are there people in your life who would care, whom you could reach out to? Or people who reach out to you? When I'm down / depressed, this is the LAST thing in the world I want to do. But are there friends of yours who also have these types of cycles? They might be the ones to just mention it to. I did that and, unexpectedly, a couple of mine jumped and called and wanted to help and I sort of couldn't believe it.
Just a few thoughts. I'd like to hear more from you though. What are you thinking? Are there stressful events happening? Are you thinking about a particular event / thought over and over? Do you exercise (also, lame-ish advice, but so incredibly helpful -- my gym, and the guys I boxed with, were my saviors during a soul-crushing job).