Although we think our actions stem from our feelings, in fact our feelings often stem from the way we act. – Gretchen Rubin

This one works. When I feel sluggish but I don’t want to feel that way any more, I go for a run. It might not be a great run, but I’ll feel much better. It’s along the lines of “Fake it until you make it.” Then when you actually feel happier it’s an awesome turn of events.