'And every man who takes part ('strives') in the games exercises self-control in all things. Now they do it to receive a corruptible crown, but we an incorruptible.'
Furthermore let them recognise that all runners or others who strive in the games exercise self-control. They discipline themselves in preparation for the games. They discipline themselves while partaking. They keep themselves under control and put everything into achieving their goal. And if people will do that in order to obtain a corruptible crown, how much more should those who seek an incorruptible.
The idea of self-control ties in with the previous ideas of being willing to abstain from things for the sake of the Gospel, even though they are 'legitimate', things such as eating in the temples meat sacrificed to idols, to which he will come again shortly. Or the participation in the pleasures of life. He is not a killjoy, but nor will he let anything unnecessary hinder his fully serving Christ. Time taken up in pleasure is not available for spiritual activity.
'Now they do it to receive a corruptible crown, but we an incorruptible.' What was the reason that these athletes in the Isthmian games, held biannually near Corinth, went to such extents and sacrificed so greatly? It was to win a fading crown. For a while they would be widely popular, but then they would be replaced by others, and forgotten by all except possibly those in their own neighbourhood. They would become has-beens. How much more then should the Christian be willing to go to extremes in order to win a crown that will never fade, that will never be forgotten, that will shine as the stars for ever.