Have you ever felt a race slipping away from you after a strong start? Have you been passed, or run out of gas, just a mile or two from the finish line? Every runner can benefit from increased endurance. Tempo runs are just the thing to help you become better at running faster for longer periods of time.
Without a doubt, the easiest way to avoid a crash after the post-race high is to pick a new goal. Decide what you want to tackle next -- whether it's getting faster, going further, being more consistent with your training, trying complimentary workouts, or maybe even setting your sights on a different sport altogether -- and put a plan together for how you'll go about achieving it.
Long distance runners are a bizarre group of people to those who find comfort in stillness, pleasure in overindulgence, and reassurance in conformity. I know this because I was not always a runner. There was a time that I scoffed at runners and the strange counterculture of running. But, now I know better.