Skipping Recovery
When pro athletes aren't training, they're sleeping, eating, or lying on the couch—recovering. When you're not training, you're working or shoveling snow. "Even with a perfect training plan, someone who is in overdrive at work will eventually fall into classic overtraining and underperforming," says Corey Hart, an exercise physiologist for the Idaho-based Physio Performance Lab.

The Fix: Pay attention to sleep (eight hours per night), energy level, and motivation. Whenever you underperform in two consecutive workouts, reduce your training by 50 percent until you feel reenergized. Every four weeks, take a planned recovery, in which you cut back on your workout time or intensity by 20 to 30 percent for a week.