257: Are You Limiting Yourself?

So many runners are limiting themselves without even realizing it. In races of nearly every distance there are clusters of runners finishing around the even numbers? Half marathoners cluster around 2:00, but also 1:50 and 2:10. Marathon runners cluster around Boston qualifying times as well as every 10 minute mark. Why is it that arbitrary numbers allow runners to group up? If the numbers really are arbitrary, are you putting a limit on yourself just because yo...