Don't failing to measure up to my calling

1 Cor 9:15-27
I would rather die than have anyone deprive me of this boast.
What them is my reward? Just this: that in preaching the gospel I may offer it free of charge, and so not make use of my rights in preaching it.
Though I am free and belong to no man, I make myself a slave to everyone, to win as many as possible.
I beat my body and make it my slave so that after I have preached to others, I myself will not be disqualified for the prize.
 In a race...: The Isthmian Games were held every three years at Corinth. Each competitor underwent 10 months' stiff training, hoping to be crowned with the victor's pine wreath.
Why?
Paul was afraid, not of losing his salvation, but of failing to measure up to his calling. Hence the need to keep striving for the goal, and not throw salvation away.
Paul was obey his calling from the Lord, he is free but like to be a slave of the Lord to preach gospel. Paul pursue the reward in heaven so he make himself a slave to everyone to win their heart for the Lord.
Appreciated Paul let us may be a Christian with correct concept and right way to living  in the world.
How?
Devotion to the Lord like Paul, and do my best on the way of my calling.