“The real duty of worship is not the outward duty to say or do the liturgy. It is the inward duty, the command—‘Delight yourself in the Lord!’ (Psalm 37:4).
The reason this is the real duty of worship is that this honors God, while the empty performance of ritual does not.
If I take my wife out for the evening on our anniversary and she asks me, ‘Why do you do this?’…the answer that honors her most is, ‘Because nothing makes me happier tonight than to be with you.’
‘It’s my duty,’ is a dishonor to her.
‘It’s my joy,’ is an honor.
How shall we honor God in worship? By saying, ‘It’s my duty?’ Or by saying, “It’s my joy?’ ”
~ John Piper