I made so many.
1. I ran too fast on distance days. We "raced" too many workouts, left many a good race on the practice field.
2. I failed to keep my mileage up during track season and I would fade as the season went on. My track season were always backwards, killing in March, garbage by May.
3. I didnt really embrace track until college. I tolerated it. I was an XC guy through and through.. I didn't realize until college that I had it all backwards. Track is where it's at.
4. I was undisciplined in my racing. I would get too competitive and involved in the race, and not stick to my race plan/pace.
5. I simply raced too much. Part of this was on my coach, but.. I would do road races in the off season, stuff like that.
6. Didnt run enough mileage (this is related to running practices too hard.) Had I chilled out, then I could have handled more miles but because it was Hammer Hammer Hammer Gas Gas Gas! all the time, there was no way I could hand more.