I don't want to sound dismissive to your question (because it sounds important) but I think a bit more information would be useful if you want a relevant answer.
From what you've said so far, I think it's in your best interest to just be up front and honest about the situation and where you stand. If they see you in a way that is different to how you see yourself, they might be unaware that a change has occurred or they might just not care. There's nothing wrong with saying "Hey, I get the feeling that you think I'm {Insert Specific Situation} but I've changed since then, I don't feel comfortable going back to that. It's just not who I am anymore." That way they can either accept it, or reject it.
I get that I'm being a bit cold about your prior relationship with this person (you said they're important to you), but what good is a relationship with someone where you feel like you can't be yourself? Or that the you that you want to be isn't accepted? You deserve better than that. At least you gave it a chance? And I'm not saying if they give you resistance then you turn tail and walk away, put in whatever fight you want to put in for this person. It just might be prudent to accept things can't continue forward in a mutually beneficial way (it's not doing them good to have you "put on a face" for them either).
I'm not sure what you're comfortable posting on here, if you really want specific advise but don't feel comfortable talking freely on the forum, you can shoot me a PM and I can give you my two cents? Whatever you wanna do.