I remember Lewis driving home the point somewhere to the effect that it is rather a matter of embarrassment for us, how much more resource we can suddenly find of ourselves underneath the crack of a driving whip than we manage to find in our motivations of what we think we should love. Not that I think this is at all any model for service to God and I wince at the comparison. But his point wasn’t about the necessity of whips at all - it was about our human nature when it comes to self-appraisal of what we can do.
A more positive comparison might be what we already have at hand to ourselves if we’ve had experience in the world of romance. Percy Sledge in his song “when a man loves a woman” showcases it well … “will spend his very last dime” … “will sleep out in the cold and rain if she thinks that’s the way it oughta be…” In short - it’s amazing how much we decide we can do once real love takes hold. We’ll move mountains or die trying.