Maturity? Overreaction?

Sometimes I forget that I'm entitled to my own opinion and that I have the right to make my own choices. Perhaps I'm too nice, or perhaps people see me as spineless. Either way, I've been noticing lately that some people treat me as more of a doormat, a stepping stool towards their own devices, than a friend. The sad part is, I had grown complacent to the newer, nicer me. But at this point in time, I do not know if being that person is going to get me anywhere as far as respect goes. I guess you can say there's been a tumor on my demeanor for a few years, and it's turned cancerous lately. Do I cut it out, or do I treat it?