I have to watch what I eat because foods I eat can stabilize my moods or exaggerate them. A high protein low carb diet with small snacks or meals every 3-4 hours will over time reduce my swings. I also avoid alcohol and recreational drugs because those can really increase depression.
Other lifestyle changes that help me are doing yoga, exercises, mindfulness, calm music, and being active on Psych Central.
Many people who are actively involved in Psych Central find it helps take them out of their own problems to develop empathy for others. And their problems though still there are more manageable.