I wrote:
The moral of the story is that you should control the amount of your favor to others.
It wants to say that you shouldn't do much favor to someone, because they may ignore or forget your favor...
It can also mean when you care too much about someone, he/she may find your favor your duty or as an ordinary thing.
How can I say the bold part in a natural and idiomatic way? Or what are the related phrases to this point?