To give for giveness sake means to give without expectation of anything in return. When you give, give without expecting a gift back...not even a thank you.
This goes for gifts of money, time, and love.
Now, if you've given a lot to the same person and they never give anything back or say thank you, you can feel it inside when you are no longer able to give to them for giveness sake.
At that point, it's time to stop giving to them. This will save you resentment towards them, and it will save them the future gift of guilt from you.
It's much easier to not do something that you feel you will regret than to do it. If you do it anyway, you will not only regret it later, but will also have to forgive yourself for knowing better all along.