The idea of repaying someone for a kind act is in itself problematic. Are we supposed to keep even tabs? Are we supposed to just do general good in the world in order to repay the world for the kind acts done to us? Should repaying have no place in our psyche?
I think, well, I actually don’t know exactly what I think about all of those questions. But one thing I know. Often when I do something nice for someone, to me, what will make me very happy, is if the person shows appreciation.
I grew up in a home where we learned to say thank you easily. We thank our mom for every single meal she makes. And we generally try to thank each other for things. I think it is important to train yourself to be used to noticing when someone does something nice for you and make sure to let them know that you noticed, by thanking them.
P.S. Of course you cannot expect a thank you from everyone all the time but I think it’s good to strive towards showing appreciation as much as possible.