This Delphic Maxim advises us to do our best. Apollo was a patron of excellence. A race, or indeed any competition, is where we must commit to winning. Even if we do not win, we have both honored the spirit of the race, but we have also learned something about ourselves and how we can better or performance.
The corollary understanding about this maxim is to press forward instead of quitting too soon. We all know someone who loses at everything because they choose not to apply themselves. Here, the maxim reminds us all that wise are those who choose endurance and tenacity. Cross the finish line.