Humility consists in three things: penitence/confession, forgiveness, and right worship.
In his treatise on humility Saint Bernard names three levels of truth as the sources of true humility.
1. Consider and admit one's own wretchedness => confession and penitence.
2. Have pity on the wretchedness of others, in light of the consideration of one's own wretchedness => fraternal correction and forgiveness.
3. Purify the eye of one's heart to contemplate heavenly and divine things.