In all of Paul's letters his love for the gospel is evident. Here in 1 Corinthians we see this passion come through in chapter 9 as he boasts of sharing the gospel free of charge in order that any and all might be saved. He would do anything for the sake of the gospel.
"So I do not run aimlessly; I do not box as one beating the air. But I discipline my body and keep it under control, lest after preaching to others I myself should be disqualified." 1 Corinthians 9:26-27