Jamieson, Fausset and Brown on 2 Peter 1:6

6. Greek, "And in your knowledge self-control." In the exercise of Christian knowledge or discernment of God's will, let there be the practical fruit of self-control as to one's lusts and passions. Incontinence weakens the mind; continence, or self-control, moves weakness and imparts strength And in your self-control patient endurance" amidst sufferings, so much dwelt on in the First Epistle, second, third, and fourth chapters. "And in your patient endurance godliness"; it is not to be mere stoical endurance, but united to [and flowing from] God-trusting [Alford].