Every contest has a prize. But Christians have the most unique crowns of victory possible. Their crowns of victory are the people that they have invested in on Earth whom they will meet in heaven. Rewards for faithful service are one thing, but the joy of investing in another human being is quite another. If we love that human being, the best thing for us is to see that person benefited. So Paul made the striving after rewards very personal.

4:1 Therefore, my beloved brethren whom I long to see, my joy and crown, so stand firm in the Lord, my beloved. (Phil 4:1)

He indicated that he very much wanted to see them and enjoy their company. They were his crown of reward. That again emphasizes the relational aspect of Christian rewards. That was why Paul said in 1 Corinthians 13 that if we make a tremendous sacrifice and have not love for the people we are sacrificing for, it profits nothing. So are we investing in people or just pursuing a heavenly reward? To do the first is to do the other because both are the same thing.