The point isn't to make other people change, it's for you to accept things as they are and not let it bother you, assuming the things that bother you that other people do aren't in fact harming you but you just don't like them. I know this is way easier said than done, but framing it properly might help. Problems will always be there in life, it's how we react to them that's the problem for us.
You can't change anyone but yourself
So you need to learn not to let other rule your life, it only harms you,
You need to say what you need to say and leave it there, move on
Learn to laugh at life and take it less at you and just being life
Bottom line, don't let others rule you, you see what it did to you, you have to look after you
I couldn't agree more with the above posters, like they said, the ONLY person you can change is YOURSELF. You need to work on finding the strength to not let things that others do affect you so severely. You need to learn how to pick and choose the people you will associate with, and that also means learning how to set the bar high for yourself in terms of how you demand to be treated. A lot of times in situations like these, there is a self esteem issue. If that's the case, there's another issue to add to your list. Also, if people KNOW that you are the way you are, they will take advantage of you, and treat you like a push over pretty much. When you start setting more firm boundaries, that will stop. People usually only try to do things they know they will easily get away with, you need to take that power away from them.
It sounds like you've already made some significant progress for yourself, so I have confidence if you work at it and set your mind to it, you can improve this situation for yourself.
I would also recommend looking into picking up a few self help books about how others treat you, self esteem, self worth.
Best to you, keep in touch!