I try to meditate (most common 'way' is to try to think of nothing for an extended amount of time) and if that doesn't work, I start holding my breath. Sometimes I'll hold my breath intermittently while going for a walk.
Of course these are temporary solutions are best, and completely worthless at times. My only salvation is to hold out until my mood picks up again. If I really can't deal with it, I just start drinking. Sometimes this amplifies the bad feelings, but most of the time it just numbs me and makes me more hedonistic so I highly don't recommend it.