Adequate sleep, eating well, getting out in the sun, socializing and doing things like volunteering or participating in my community garden, meditation or other mindfulness things like walking in nature, exercising when possible. I don't do it too much, but doing creative things like painting or music can help me, too, especially if I am dealing with something emotionally difficult. These might sound like cliche answers, but if I do these often enough it makes a difference. I don't do them all every day, but do my best to do them throughout the week. Give me lack of sleep, poor diet based on caffeine and sugar, social isolation and/or lack of sun and it's a recipe for a dark place for me.