I need some advice, I seriously want to break the school record (15:29) in the 5000m but every time I race I always fall apart/cramp up and run close to tempo pace over the last 800m. For example, this last race I was running very even splits in 74 seconds and feeling great, until the last 800m I couldn't run straight because of a massive side cramp and ended up finishing in 15:39. It is just very disheartening knowing I'm in better shape. Any suggestions on how to get over this?
For some backround info, I run around 80 miles a week and my other pr's are 2:00(800m) 3:58 (1500m) 8:38(3k) and 25:34 (8kXC)