Working Out Just to Work Out
Your training should support the physical demands of your sport. Doing Olympic lifts to failure won't improve your climbing endurance. Long-distance jogging doesn't build the anaerobic capacity that hockey players need. And doing only two-leg strength exercises in the gym doesn't make sense for start-and-stop sports like soccer, since running is an alternating single-leg activity.
The Fix: Make sure your workouts train the muscle groups you need. If your sport involves running, do some single-leg box jumps. If you're an endurance biker, you need to convert some fast-twitch muscles to slow-twitch, so be sure to do the occasional weekend tour in which you ride all day at a leisurely tempo. And unless you're a powerlifter, don't lift weights to failure: it'll just make you sore the next day.