11 But now, when “the flesh lusts against the Spirit, and the Spirit against the flesh,” is the contention of death; we do not what we would. Why? Because we would that there should be no lusts, but we cannot hinder it. Whether we will or not, we have them; whether we will or not, they solicit, they allure, they sting, they disturb us, they will be rising. They are repressed, not yet extinguished. How long does the flesh lust against the Spirit, and the Spirit against the flesh?
Will it be so, even when the man is dead? God forbid! You put off the flesh, how then shall you draw the lusts of the flesh along with you? Nay, if you have fought well, you shall be received into rest. And from this rest, you pass to be crowned, not condemned; that you may after it be brought to the Kingdom. As long then as we live here, my brethren, so it is; so is it with us even who have grown old in this warfare, less mighty enemies it is true we have, but yet we have them.
Our enemies are in a measure wearied out even now by age; but nevertheless, wearied though they be, they do not cease to harass by such excitements as they can the quiet of old age. Sharper is the fight of the young; we know it well, we have passed through it: “The flesh” then “lusts against the Spirit, and the Spirit against the flesh; so that you cannot do the things that you would.” For what would ye, O holy men, and good warriors, and brave soldiers of Christ? What would ye?
That there should be no evil lusts at all. But ye cannot help it. Sustain the war, hope for triumph. For now in the meanwhile ye must fight. “The flesh lusts against the Spirit, and the Spirit against the flesh; so that you cannot do the things that you would;” that is, that there should be no lusts of the flesh at all.
Source: Sermons on Selected Lessons of the New Testament (New Advent)