When someone shows you who they are.. do you believe them?
Or do you think they will change.. maybe you made a mistake and they aren't really that way.. maybe it's your fault? Or do you cut and run when they do that?
It's a dangerous place, emotionally, to hope that people will change into a version that we'd like them to be. It definitely would be my fault if I chose to ignore what was in front of my face in favor of a fantasy. Do I cut and run? It depends on the nature of the behavior, I suppose. There are qualities I can choose to accept, if they are not harmful to myself or others. Some people are toxic, though, and I generally don't keep them around for long.
I try to take people at face value. None of us is perfect and there are some imperfections in other that I can overlook and others that I won't/can't. In terms of a romantic relationship, if someone thinks they are going to change you or if you think that, you aren't being honest with them or yourself. We are who we are. A very few of us are happy to change to comport with what someone else thinks we should be. Imagine living the rest of your life not as the person you truly are, but the person your significant other expects you to be. After a while, neither of you is going to be happy.
I keep my own council on who or what people really are, I weigh what people say about themselves against what I observe. Showing me and telling me are two different things.
I don’t believe there are many people who are totally irredeemable, and everybody errs on occasion. I tend to dispense forgiveness sparingly. I also think it is foolish to apply our expectations to others, and a form of servitude to live our lives on the expectations of others.