I think people can change somewhat by altering their perspective on life.
If we are talking about change being a good thing then perhaps we don't change who we are/were with particular people, because those people created in us the negative personality --- but by learning the lessons and taking on board our reactions to situations, and growing, I believe we can change for the future, and that our interactions with new people, will be from a different perspective and thus create new and better realities for us
I'm a much different person than I was 2-3 years ago. Am I a better person? That's difficult to answer. I believe I am wiser and more likely in future to get the best for myself, BUT does that make me a better person in humanities eyes? Well I'm not as "available" to be a doormat as I used to be, so maybe not. Maybe humanity would view my personality change as for the worse?
I won't apologise for it though, because life has lead me down these roads and taught me these particular lessons, and if I do not learn these lessons and continue to stay the same then I continue to make the same mistakes in life...