Hone your ability to judge running effort.

The term perception of effort refers to a person’s subjective sense of how hard he or she is working relative to his or her limit during exercise. Distinct from pain, thirst, heat, fatigue, and other perceptions that are commonly experienced during exercise, perception of effort plays a critical role in running performance. The better you get at judging how close you are to your limit at an given moment in a race, the closer you will come to finishing each race in the least amount of time physically possible. No device, test, or calculator can do that for you; it must be done by feel.