I'm guessing you have already done this, but if not - have you looked into "codependency" as a mental health issue?

"Caring too much about people being happy" is pretty much the definition of a codependency problem. It's possible to get past it without turning into an asshole.

There's an excellent book on it - http://www.amazon.com/Codependent-No-More-Controlling-Yourse...

May not be of use, but I thought I'd comment in case it is!