How did the Olympic athletes train for their races?
They trained repeatedly and consistently, yet with temperateness. They did not destroy their bodies by overtraining, nor did they come to the race flabby and in no condition to run. With common sense and self-control in all things, they prepared for the Olympic races.
Les explains that Paul is alluding to the Olympic athletes. They trained, and they trained, and they trained, but they did it with temperateness. They did not destroy their body with over training, nor on the other hand did they come flabby and in no condition to run the race. So with common sense and being temperate in all things, they prepared for these Olympic races. Paul tells believers the same thing: athletes do it to obtain a corruptible crown, just a wreath of leaves that dries up, but believers run for an incorruptible crown that will never end.
And every man that striveth for the mastery is temperate in all things. Now they do it to obtain a corruptible crown; but we an incorruptible.