Also, if someone says "my ex was mentally ill and that's part of why we broke up," that may well be true—just as it may be true that a particular relationship didn't work because of distance, or because one person wanted children and the other didn't. But mental illness doesn't mean "cannot have a good relationship" any more than "wants children" or "lives in Seattle" does. If someone says "women are crazy" or refers to all of his (or her) exes as crazy, that's a statement about the speaker, not the people they have dated.