From E.J. Carnell’s Christian Commitment as quoted in Desiring God by John Piper:
Suppose a husband asks his wife if he must kiss her good night. Her answer is, “You must, but not that kind of must.” What she means is this: “Unless a spontaneous affection for my person motivates you, your overtures are stripped of all moral value.”
How many times have I failed as a husband on this account? “Do I have to help you wash dishes, fold clothes, pick up the living room?”
How many times have I failed as a believer on this account? “Do I have to sing during worship? raise my hands? give financially?”
Am I teaching my kids to avoid the same mistakes? “Daddy, do I have to pray? forgive my sister? obey Mommy?”
The fact of the matter is that I should be internally motivated to do these things. If I am waiting for an external motivation (or perhaps even acting out of that external motivation) I have missed the point and my actions are in vain.
Let that marinate a bit…