This is our [reason for] proud confidence: our conscience testifies that we have conducted ourselves in the world [in general], and especially toward you, with pure motives and godly sincerity, not in human wisdom, but in the grace of God [that is, His gracious lovingkindness that leads people to Christ and spiritual maturity].

Working together with Him, we strongly urge you not to receive God’s grace in vain [by turning away from sound doctrine and His merciful kindness].

If I must boast, I will boast of the things that reveal my weakness [the things by which I am made weak in the eyes of my opponents].