Paul founded the church at Corinth. After he left Corinth, various false apostles passed through town. These traveling preachers built up their own ministries (and their wallets) by pointing to their own "impressive" credentials rather than pointing to Jesus. By comparing Paul unfavorably to themselves, they undermined his position as father of the church in Corinth. More important in Paul's eyes, they were undermining the true gospel and leading people away from the Lord (2 Cor 11:3ff).
The Corinthians, in their foolishness, demanded that Paul once again "prove" his apostleship. In today's first reading, Paul sarcastically "stoops" to their level in defense of the gospel he preached. Notice that Paul uses the word "I" eighteen times. To Paul, this emphasis on self is "insane" (2 Cor 11:23). To be insane is to be completely out of touch with reality. The ultimate reality is that Jesus is Lord of heaven and earth (1 Cor 12:3). Everything in heaven revolves around Him (see Rv 4:8ff). The angels revolve around Him (Jn 1:51). Likewise, the earth, since it belongs to God (Ps 24:1), was created to revolve around the Son.
My mother likes to say, "The earth doesn't revolve around me." To St. Paul, this is the beginning of sanity. When we take our "eyes" off of "I" and fix them on Jesus (see Heb 12:2), our eyes are sound (Mt 6:22) and we are sane.
Die to "I" (see Lk 9:23). Live for Jesus (2 Cor 5:15).