For many children there is a huge fear in being forgotten, especially if your parents have done it before. For example, I'll never forget waiting outside of my elementary school building for over 2 hours waiting for one of my parents to pick me up. They had gotten busy and had forgotten me. (Well, I guess they are in good company because even Mary and Joseph forgot Jesus one time in the temple when He was 12 years old.)
And then when we grow older and start playing sports or working our first job, we want our coach and employer to not forget about our hard work in practice or on the job. And when we come to the end of our life, we don't want to be forgotten. We want to be remembered.
So here's the great news, when you are "working for God" and serving Him by serving others: GOD WILL NOT FORGET ABOUT YOU AND YOUR LABOR FOR HIM. "For God is not unjust to forget your work and labor of love which you have shown toward His name, in that you have ministered to the saints, and do minister" (Hebrews 6:10).
So the next time you are working hard for God and serving someone who is ungrateful, DO NOT FEAR THAT YOUR LABOR OF LOVE WILL BE FORGOTTEN BECAUSE GOD HAS A GREAT MEMORY.