C.S. Lewis emphasizes the distinction between "being in love" and love itself. The initial passionate feelings of being in love are fleeting, while true love is a commitment that transcends emotions. It is a unity between partners that relies on willpower and conscious effort, further supported by faith and divine grace, particularly in Christian marriages.

This enduring love is what sustains a marriage over time. While the excitement of being in love initiates the relationship and prompts vows of fidelity, it is this deeper, more stable form of love that ensures those promises are honored. Thus, the essence of a lasting marriage is rooted in unwavering love, not just the transient feelings that may fade.