Are All Music Teachers As Dense As I Am?

Another message from my ex-husband, he wants my help.  That was our entire relationship.  He wouldn't do something, or couldn't do something and at the last minute, I would be expected to fix it.  Every year, his portfolio review would come around, and at 1am the day before it was due, I was sitting up printing and gluing and correcting text.  I edited all his papers.  I practically did all the research and wrote them, too.  

This time, I told him no.  I am not going to continue to do favours for him that I know will never, ever be returned.  That's not friendship, that's not nice, that's just using me to get what he wants and I had the opportunity to do that while we were married, why would I do it afterward?

It's not just him.  I scroll through my Facebook messages and realise, with a few exceptions, people only contact me when they want me to do something for them.  "Hey, I bet you know," "Could you look up ...?" "Give me an idea," and I do.  Sometimes, when they've gotten what they want and say thank you, I say, "Hey, we should do a thing," and they say, "Yeah, yeah, sounds great."  And it never happens.  

I wonder how to change this, but I suspect that it involves being a person that I'm not OK with being.