I believed whatever nice things done to others is returned to you in one way or another. This,however, does not necessarily mean that "that" kindness has to come from those whom you had shown kindness to. I understand how you feel, Michael. Many times I've been into situations you are now.
Kindness is one of my virtues. Very kind that often times I did not notice that I am already used and abused. I was hurt as a result and learn my lesson.
Set limitations for whatever you do and envision whatever consequences they might bring if you go beyond limits. The pros and cons of it. Sometimes, being "unkind" could bring goodness to the person whom we denied kindness.
God bless you, Michael.