I used to feel the same way, but you have to realize that you shouldn't do workouts beyond your current fitness level. If you want to run, say, 16:30 then do your 5*1000 in 3:18.
This will help you in two ways-first you'll be less tired for races and second your body will feel comfortable going the race pace. You are doing the workouts of a 15:30 person. When your body realized it can't sustain that pace for more than a mile you have nothing to fall back to.
Anyway, it's not necessarily a psychological issue, I used to be this way to and people thought I was a headcase, but I really was just training over my head.