From St. Gregory Palamas (The Homilies Vol. 1: Homily Two para. 8; St. Tikhon’s Seminary Press pg. 13):

“Thanksgiving for the benefits received from God is made acceptable by humility and not looking down on those who lack them. It is rendered unacceptable, however, by being conceited, as if those benefits resulted from our own efforts and knowledge, and by condemning those who have not received them.”