I feel like all the heavies are weighing in on the themes of Romans 8 and the deep work of the Spirit to empower Mortification Through Joy... here's Jack:

"Where can you taste the joys of obeying unless He bids you do something
for which His bidding is the only reason?"
(C.S. Lewis, Perelandra, Chapter 9)

"A perfect man would never act from sense of duty; he'd always want the right thing more than the wrong one. Duty is only a substitute for love like a crutch which is a substitute for a leg. Most of us need the crutch at times; but of course it is idiotic to use the crutch when our own legs can do the journey on their own."

(C.S. Lewis, Letters - 18 July 1957)