Dictionary.com has several slang definitions for doomat which include a person who is the habitual object of abuse or humiliation by another, one who submits meekly to domination or mistreatment by others, and a person who is physically weak and ineffectual. I have fit all of these descriptions at some point in my life and sometimes still do. It can be very difficult to go against one's innate nature, and just because one speaks up doesn't mean one will be heard or even taken seriously. I have learned the hard way that "sometimes being a bitch is all a woman has to hold onto" to quote one of my favorite movies, "Dolores Claiborne."
There are always choices. Some people are better at making good choices than others. One can only try to do what they feel is best at any given time, but it doesn't necessarily always turn out the way we'd imagined.
In the first paragraph, I used terms that I'd read in this very forum, two of them from the thread on verbal humiliation. The prejudice is insidious and unlikely to offend the majority. The minority it does offend are unllikely to speak up, but I'm doing it now.
Many people do need to get off their asses. However, I think it takes a strong person not to give in to the peer pressure to be something she isn't. One can run themselves ragged trying to do whatever it takes to find happiness, especially when one is told to be more outgoing or to do this or that, instead of just being themselves and being happy.