The Heavenly truth that God will give believers eternal rewards should motivate us in doing ministry.
Randy Alcorn put our grumbling in ministry in perspective:
What a motivation this is when we feel our labors are unappreciated by others! We can be freed frmo the burden of concern about whether others overlook our deeds, because God assures us that he will not overlook them. When we understand what it means to be promised a reward from God, any prospects of rewards from others–or any bitterness for not being rewarded by them–will shrink in comparison.” (Money, Possessions and Eternity, page 129).