Paul has a tender affection for the Corinthians. They hold a special place in his heart. And although he has rebuked them for their sinful, shameful behavior, he also wants to see them flourish in their faith. So as their spiritual father, he uses all of the resources at his disposal to set them on the right track. He urges the Corinthians to follow his example in living out the Christian life.
In the presence of growing divisiveness and factionalism within the church at Corinth, Paul addresses the issue fueling it all- the Corinthians' pride. Using sound reasoning and at times biting sarcasm, Paul equips the Corinthians with the tools and resources necessary to kill their pride.
In the latter half of 1 Corinthians chapter 3, the Apostle Paul seeks to simultaneously warn the Corinthians about their destructive divisions but also encourage them to use their lives for the Kingdom of God. No one who lives for Christ and his glory, seeking to edify the church and spread the Kingdom of God wastes their life. On the contrary, each one shall be rewarded by God. As Christians, we should live with an eternal perspective, using our lives to store up treasure in Heaven and frequently remind ourselves of the incomparable glories yet to be revealed to us and experienced for all eternity. Let none of us waste our lives.