Run your own race at an even pace. Consider the course, the temperature, the weather, and most importantly, your current level of fitness.
Happy people don't run a 3:47 mile.
Road racing is rock 'n roll; track is Carnegie Hall.
Overtraining is the biggest problem incurred by runners who lack the experience or discipline to cope with their own enthusiasm.
You've got to be a little bored to be doing really good training.
There's no satisfaction without a struggle first.