Run the mile that you're in. Especially for longer races (but even for short ones, like 5-Ks), it can be tempting to dwell on the total distance or on how far you are from the finish line. Try not to. Instead, focus on the mile you're running at that particular moment. Be mindful of the full distance, of course; mentally and physically, you should be aware of how far you've got to go. Primarily, though, keep your head in the here and now. That's a nice metaphor for life, too, by the way. In case you were looking for one.