Luke 6:35-36
But love your enemies, do good, and lend, hoping for nothing in return;
and your reward will be great and you will be sons of the Most High.
For He is kind to the unthankful and evil. Therefore be merciful,
just as your Father also is merciful.
I experienced major disappointment last week that is, unfortunately, frequent with me, and I think most people experience this problem, too. It's when you are doing something that has some benefit for another person, and they don't respond with any appreciation, either because perhaps they don't appreciate it, or perhaps don't appreciate as much as you think they should; or if they do appreciate it, they aren't able to show their appreciation. It's the universal problem of giving but getting anything in return. One of the biggest regrets of my life, is that the people who did the most for me, I didn't show enough appreciation. Disappointment is a very bad feeling, not only for the person who is disappointed in the other, but for the person who does the disappointing.
The deep feeling of disappointment is caused by expecting something in return in the first place. When you expect something in return it doesn't happen, because that expectation is wrong. I think you have to try to give your most and best to everyone, and expect nothing in return from that person. If one does that, God will reward that person in better ways than if the unappreciative person had given something in return. As I heard someone say recently, "You can't out do God."
However, I still think it damages a relationship when one person can give more than the other person. I think that means that the people aren't evenly matched for a successful relationship, and they both should just move on. But, you shouldn't hate each other, but just understand that's the way it is. Everything in life evens out.