This is linked with Mosiah 2:17 which says "…when ye are in the service of your fellow beings ye are only in the service of your God." We are fortunate enough in The Church of Jesus Christ of Latter-day Saints to be given the opportunities to serve others and, therefore, serve God.
I love this quote because it really outlines why we should give service. However, it also makes me think of how indebted we are for the greatest service ever given, that was given by our Saviour. He didn't perform the Atonement for His sins – He didn't have any! Neither did he do it for glory – He gave that glory to the Father (see Moses 4:2). He did His great work because He loves us. No matter what service we give back to the Saviour, we still "…would be unprofitable servants…" (Mosiah 2:21).
Humbling words. In the end, no matter what we give and sacrifice, we can't repay our debt to the Lord. Even if there was some way, the Lord pours out more blessings to us as we sacrifice, so even then our debt just keeps on getting greater!
In conclusion, we are told some relieving news by King Benjamin in Mosiah 2:22 "…all that he requires of you is to keep his commandments…therefore, if ye do keep his commandments he doth bless you and prosper you." The Lord is happy with our efforts as long as we strive to do our best – as long as we recognise truly that without Him, we would always fall short.