A man is very apt to complain of the ingratitude of those who have risen far above him.

When someone you once helped ends up far ahead of you, a complaint tends to form on its own: they have forgotten what you did. Sometimes that is true. Often the grievance grows in proportion to the distance between you rather than to anything they actually failed to do. What stings is the gap, and gratitude is the language available for saying so.

If you find yourself keeping a ledger on someone who has done well, look at the ledger honestly. Ask whether you want acknowledgement or want the distance closed. Naming the second thing privately takes most of the heat out of the first.