I too gave up being "a nice women" in my 40s and it's the best thing I've ever done for myself. I'm still kind, gentle, helpful, considerate, etc., but I'm no longer going to be the grown up version of "a good girl" which essentially means a compliant one, easy to push around and control. I think the more you embrace this, the less push back you will get. Some always, to be sure, but few people have any expectations of "niceness" from me any more so they aren't really shocked when they don't get it.