Add Yahoo as a preferred source to see more of our stories on Google. You know you always feel better after working out—and this alone should vanquish any of that couch-laden inertia. But we're human.

'Five more minutes,' you whisper to yourself as you hit the snooze button and roll over. You were supposed to be at the gym 10 minutes ago, pounding through a set of biceps curls. Instead, you’re ...