When You're Bummed

Exercising releases a fair amount of endorphins that can pull you out of a funk, but depression and mental exhaustion are the hardest moods to overcome—in terms of getting to the gym in the first place. "You feel less interested in everything, which can make blowing off exercise that much easier to do," says Huff.

Schedule just 15 minutes. Mentally preparing yourself to do only 15 minutes can help you through long workouts. "It takes at least that long for the endorphins to do their job," says Huff. "After 15 minutes, you'll likely feel better and go ahead and do the full workout—but you'll have the freedom to go and stretch if you want."

Don't rest. "In one sense, more rest only gives your mind even more time to dwell on whatever's upsetting you," says Butryn. Instead, lighten the amount of weight you typically lift and switch to higher reps with less time between sets—30 seconds, maximum. "Speeding up your weight workout will still give your muscles a workout, while creating enough of a distraction for your mind," Butryn says.