True devotion should have joy in it.  There is nothing more pathetic than those whose religion is without joy.  Piety without joy can be legalism or self-worship.  Such persons are captives of a toxic faith.  They are slaves to forms that have, long since, lost meaning.  If we love the Lord, it is a joy to do His work and to wash the feet of His disciples.  If we are doing it to get a promotion, then joyless vanity follows.  We are left empty.  Love the Lord, and serve Him with gladness.

“But now we are released from the law, having died to that which held us captive, so that we serve in the new way of the Spirit and not in the old way of the written code.” Romans 7:6 (ESV)