When you have the notion that high moral acts must be free from self-interest, then worship, which is one of the highest moral acts a human can perform, has to be conceived simply as duty. And when worship is reduced to a duty it ceases to exist. One of the great enemies of worship in our church is our own misguided virtue. We have the vague notion that seeking our own pleasure is sin and therefore virtue itself imprisons the longings of our hearts and smothers the spirit of worship. Worship is an inward feeling and outward action that reflects the worth of God.
Worship is vain, empty, nothing, where the heart is unmoved.
And I think it's possible to describe in general the experience of the heart in worship. There are three general ways that the heart can respond in worship to God and they usually overlap and coexist. The heart can delight in the wealth of God's glory. The heart can long for that delight to be deeper and more intense and more consistent. As a hart longs for the flowing streams, so longs my soul for thee, O God.