When I step onto a treadmill at the gym, some days I'm not feeling very motivated to push myself. I'm sure this happens to you too, so here's a suggestion from FitSugar reader smaine07. She likes to go to the gym when it's crowded so she can "compete with the person beside me."
So the next time you're on a treadmill, elliptical, stationary bike, or other cardio machine, use someone else's drive and passion to pep you up. Find someone on a machine that looks like they're working hard and pretend you're moving right along with them. It's great inspiration to feed off their fire, and you'll be surprised at how suddenly you have a burst of energy. I find that I can go longer or faster when I'm mock competing with someone else.