The best advice a coach can give is to choose your battles appropriately, focusing your hard efforts on the training days that are the most important. How many times, however, have your gotten carried away on an easy run? The run was supposed to be a recovery day from a previous hard workout and a prep for the next day's race-specific training. Instead, it became the fastest you've ever run for your loop. Congratulations! You probably just screwed up the next day's key workout and possibly set yourself up for injury later on. To avoid this error, know and adhere to the purpose of each workout. If the schedule calls for an easy day, then run easy. If it calls for a hard track workout, then ensure you are properly rested in the days before. Don't let easy days get out of hand and become hard days, because of others, your own need for your running fix or just spacing out and not noticing the increasing pace. Be disciplined.