You are absolutely right, if you do something good in your life it will come back to you.
Also because it is a chain reaction: good stimulates good and bad stimulates bad.
With this post of yours you brought back to my memory a very famous Italian writer Ugo Foscolo, where in the "Sepolcri" a verse goes like this:
"Solo chi non lascia eredità di affetti poca gioia ha dell'urna"
"Only he who leaves no legacy of affection little joy has of the urn."
Paraphrasing it says that he who does not leave a mark for the good done (legacy of affections) will not be able to rejoice when he dies.