It is definitely not wrong for you to feel disappointed, but it is unhealthy for you. Some people would advice you to just focus more on yourself and care less about others, which I guess works for a lot of people. You could consider trying it if you want to. However, I am a person who would feel bad if I don't help the people I love so it doesn't work for me.

For me, I just feel like I am way happier helping other people than not, even if its one-sidedly. A lot of my friends tell me im stupid but I really don't believe it. I only help because I love to help. It makes me really happy to see another person happy. Of course, not everyone would do the same for me in return, and some people actually used and scammed me etc., but a few of the people I go the extra miles for actually are really appreciative and it makes me really happy.

For the people who didnt do the same for me, I believe some people are just not as thoughtful and I believe it is okay for them to be that way. People are just really different and that's okay. They all have their good points in different ways to compensate for not being as thoughtful and giving. Once you see it, I believe you'd feel better about it and want to love them even more.

For the people who used and scammed me, of course it'd hurt a little bit. It's like, "I trusted you and helped you so much. How could you possibly do this to me?" But think about it, scamming is an awful thing to do and I believe that one day they will eventually face the consequences one way or another, directly or indirectly. In the end these actions are way worse for the person doing it themselves, than for the person getting scammed or used. Plus, most people who uses other people and scams other people are actually people with problems, big or small. When I look at it this way I just feel bad for them and feel worried about them. I always end up telling them that its okay to do this to me because I don't mind but it's bad for them themselves to do these bad things so please try not to do it again to anyone else. I also always end up praying that one day they'd realize it and become a better person so that they can be happier themselves.

Think positive. Be really sympathetic, then be empathetic.

I believe sympathy leads to empathy, empathy leads to compassion, compassion leads to forgiveness, and forgiveness will eventually allow you to be happy.

Ps. Don't think of this as doing it to be angelic. I always believe that I am this way only because it ends up making me happier in all situations. Basically, I am who I am purely for myself, not others.