If it's impossible unless you want to change, do you resent the other person for criticizing you? As if the constant reminder indicates your failure to do anything about it. Knowing you need to change is meaningless to the other person unless you manifest some changes. It's not enough to be your own worst critic, it actually makes the situation a bit sorrier because you know you have a problem and do nothing to fix it.
It can be, definitely. Some people are much more comfortable with themselves, or have a strong ego that needs to be assertively challenged before it will reconsider its own viewpoint.
Usually for me personally, I *was* trying to fix the flaw and pushing myself far too hard to make an overnight change, when more time was required. So when someone else pointed it out, it used to make me feel more inadequate and embarrassed... especially if they were treating me cynically.
And yes, then when I get in situations where I find myself apathetic to fixing the item in question, then I get cynical about myself. (Fun cycle.

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It seems to me that people say they want honest criticism, but when they get it they don't accept it. They find a way to wiggle out of what they know their problems are, or say someone caused them to be the way they are, not realizing that everything is cause and effect. You can't just isolate behavior and assign blame.
I think we all do this to some degree -- it is a human temptation. And I don't even think it's an inherently bad thing, it's simply the "give and take" between the ego and the externalized world. To do ANYTHING in life, we have to develop a secure strong ego that believes in what it's doing; and naturally, the ego pushes back when challenged. A healthy ego is able to believe productively in itself and have ambitions, but be able to listen and integrate constructive criticism without outright rejecting it. What you describe is sort of the "ego gone wild" or wandering off-track.
And when the ego feels undeveloped or weak, you end up more where I was at, where the ego is unduly impacted by external criticism and constantly hamstrings itself in trying to comply, never totally trusting its own values and strength.
I remember I was when I was a teenager and I went with my parents to the grocery store. They got into an argument in the car before entering the store. When we got into the grocery store, my father asked my mother a question and she snapped at him and walked away. I was pushing the basket and my father turned to another man and said, "see how she treats me, all I did was ask her a simple question." The man nodded his agreement and started talking about his wife, blah blah blah.

It just makes me ill when I see that sort of thing happen around me.
I always think about this when people say they want to change or don't want to admit something's their fault. It's so easy to walk into a situation, see one thing and say well you're the cause of this. You have no knowledge of preceding events, why the person has become the way they are. It's like all this stuff gets swirled and entangled together, people say you did this and they're right, but you turn right back around and say, well you did this which is why I did what I did. When will this foolishness stop? When is someone going to be mature and say, you know, I can only be responsible for what I did.
Well, I am a parent of three children... so... *groan* ... yes, this is the typical lecture that we give when we get the daily arguments of "But he said....!" and "But she did....!" It's a long process. And some people weren't forced to learn to do this as children, so now they have to learn it as adults... when they're no longer in submission to higher authority and HAVE to learn it.
I'd think that if you really want to change, you'd start showing change, especially if you care for the other person. I'm not saying a complete 180 is less than 24 hrs, just some results of your desire to change, and acknowledgment of your faults would prompt some things to happen faster than others.
True. I agree with both. One needs to have patience, because the process of change is long; one also needs to accept that "signs of good faith" are very helpful in terms of helping one change AND signaling other people that the change is in progress.
(It reminds me a little of the Christian "Faith vs Deeds" debate.)
Anyway, if I was in a situation like this, I would simply keep communicating daily so that I knew what the other person was thinking and committed to, and they would understand how I was perceiving things.