"To the Jews I became like a Jew, to win the Jews. To those under the law I became like one under the law (though I myself am not under the law), so as to win those under the law. To those not having the law I became like one not having the law (though I am not free from God's law but am under Christ's law), so as to win those not having the law. To the weak I became weak, to win the weak. I have become all things to all men so that by all possible means I might save some. I do all this for the sake of the gospel, that I may share in its blessings." NIV translation
Paul did not walk around with an air of superiority but instead he met people where they were in their life. He put himself in their shoes in hopes of showing them the freedom that he had in Jesus Christ. What is meant by sharing in the blessings of the gospel? The short answer is that it is a freedom from worry based on the fact that we are Christ's bondslaves.
"Do you not know that in a race all the runners run, but only one gets the prize? Run in such a way as to get the prize. Everyone who competes in the games goes into strict training. They do it to get a crown that will not last; but we do it to get a crown that will last forever." NIV translation
Now, Paul begins to answer the question of what is in it for us. He compares the Christian life and walk to the sport of running. There are many people who train for a very long time to run a marathon. There can be thousands of runners at a race but usually only one man and one woman are the winners. They run for a temporary reward such as a trophy, title, and money but that reward is quickly forgotten and in the last days will mean nothing. As Christians, Paul urges us to treat our walk with Christ with the same urgency. The crown that he speaks of is not salvation but speaks of the judgment of rewards.
"Therefore I do not run like a man running aimlessly; I do not fight like a man beating the air. No, I beat my body and make it a slave so that after I have preached to others, I myself will not be disqualified for the prize." NIV translation
Those that run a race expect a reward when they win and Paul tells us that he is expecting a reward for his service in preaching the gospel. This reward is not salvation (like many people teach) because salvation is by grace (a gift) and, here, Paul tells us that he is working for this reward. He tells them and us that he puts into practice what he preaches so that he will not be disqualified from the race and lose his reward. So, what's in it for us? We do not know what these rewards will be on the last day but we can trust God that they are worth all the things that we go through on this earth.