When we serve God, we can sing for joy  -  Isaiah 65:13-14

Therefore thus saith the Lord GOD, Behold, my servants shall eat, but ye shall be hungry: behold, my servants shall drink, but ye shall be thirsty: behold, my servants shall rejoice, but ye shall be ashamed: Behold, my servants shall sing for joy of heart, but ye shall cry for sorrow of heart, and shall howl for vexation of spirit.

The contrast between true believers and unbelievers is the difference between abundant food and hunger, between plentiful drink and thirst, between rejoicing and sorrow, between singing and wailing. Unbelievers will realize one day, all that they pursue and long for is empty and vain.