The seasons when I've run my best, I "beat" every workout, meaning that I never fell apart and rarely had to go to the well. Also, I had a pop in my step on most days.
The seasons that were crap, I went to the well on most workouts and felt tired most of the time. My workouts were faster, but races much slower.
So put me in the train at 90% and don't go over the edge category.
sub 3:44 1500.