Paul wrote these words to the Corinthians because they had a problem that is common to all people. And what is that problem? It's thinking too highly of ourselves; it is thinking the world revolves around us; or in other words, it's being self-absorbed. So what is the solution to this problem?
When I find myself self-absorbed, there's a little saying I repeat to myself: "I am the moon, not the sun." The moon produces no light of it's own. Rather, the moon reflects the light of the sun. I have to remind myself that any light in my life comes not from me, but is a reflection of God's Son, the true light of the world.
The Corinthians had trouble distinguishing between the source of light and its reflectors. This is why Paul asked, "Are we beginning to commend ourselves again?" He was reminding them that we honor God not by claiming status, but by living a life which shows evidence of belief in a God who loves all people.
A Christian's life, no matter how moral or generous, remains a satellite with no light apart from the "Son" of God. As Paul says, "the Word of Christ is written not on tablets of stone but is written on our hearts." Therefore, we need not congratulate or exalt ourselves. We are the moon, not the sun.