Christians live not under compulsion, but from a cheerful heart
"Each man should give what he has decided to give in his heart, not reluctantly or under compulsion, for God loves a cheerful giver." (2 Cor. 9:7)
I think this applies to more than just our money (which is the context of this verse), but rather our whole Christian life and service. Since God has already taken care of our eternal redemption, doing good isn't a matter of compulsion (do this or else burn!). And that creates the possibility of our freely and cheerfully giving ourselves to God, in whatever aspect of our life.