First thing I would suggest is to try to establish a pattern of behavior that will prevent most of that from becoming an issue.
What I mean is, try not to let people take advantage and disrespect your boundaries and feelings. That way you won't have this resentment building and you won't have to straighten things out after so much resentment has built up over being pushed around and taken advantage of.
It will be hard at first but it's easier and much more effective in the long run.
It sounds like right now you have this repeating pattern going on that these people (and you) are used to as being the norm. Try to change that. Good luck