Most people can race 4-5% of their mileage as races in the long-term (think seasons or years) and 8-10% in the short-term. This means that you should run at least 10 miles for every mile you've raced before you race again. Jack Foster had a rule that you needed an easy day for every mile raced and his rule becomes my rule at 70 miles per week.
Every week that you don't race, you should do a time trial. A time trial is run like a race, but without competition and without tapering. I recommend alternating between two extremely short time trials: one of 45-75 seconds (almost always 400m on a track) and one of 2.5-3.5 minutes (commonly 1200m on a track).
The rationale for these short time trials is to get used to running anaerobically. If you're racing as hard as you can, the last 1-3 minutes of the race are going to be uncomfortable; you don't have enough oxygen to sustain what you're doing, so your body, feeling that it's suffocating, demands that you slow down or stop. Pushing through this barrier is what a finishing "kick" is all about. When you practice doing these runs, they become easier and you learn that you can tolerate more than you thought you could. This can lead to picking off runners at the end of races that are struggling because they haven't done this.
It's not fun, admittedly. But it's so short that you get over it quickly. It won't wear you out the next day like a longer race will.
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