I think that you all have noticed(if have not yet , in future , hopefully you will) that "Nothing goes unpaid" in life , literally nothing ..
You may have helped a friend in extreme danger, helped a friend even though it was not yours, fed a helpless dog on the street, given up a bus seat for an elderly woman or a pregnant woman, may have comforted someone who lost a good night's sleep or may have been very upset....
Even if they don't always remember them, God or nature does. These are accumulated in nature. Things come back to you even if those you favor don't. You will see that you are in dire straits, there is no hope - some help or people will magically arrive. Because nature repays its debts in any way , We can not comprehend..
Just as nature accumulates every good deed of ours, it also keeps the bad ones. Did something bad and thought that I got over it, this is not happening. He/She may not have the power to answer whom you did wrong, but someone will answer for him.
Basically, the delight that people give, comes back in another form; In a form of another light. And whoever loathes, returns in another form. Nature owes no debt.