When I really feel like dogging it at spinning class, I engage in some self-talk that goes something like this: This is 45 minutes out of the entire day, and 45 minutes is all you get. In an hour you will be at your desk, where you’ll stay for most of your waking hours. You’ll be envious of the joggers outside in the middle of the day. It’s very unlikely that you’ll get more gym time once this 45-minute opportunity has ended, so treat it like gold.