To me, this quote is saying, do good, give, treat people right etc because it's the right thing to do, you should not expect reward from them, rather let God be your rewarder. (And no matter how hard they try to fix it, that level of trust you gave can never be fully regained ever again.)
Sometimes we learn more about someone at the end of a relationship than at the beginning.Loyalty and trust is the key here. If you don't have trust, you don't have a relationship...friendship...or whatever. “The best way to find out if you can trust somebody is to trust them.”