Perplexity in Friendship!

A true friend accepts you the way you are! But aren't true friends supposed to be your best critics?? Lately this has been a great cause of perplexity in my life :P
What is the fine line which describes when a friend is being your critic and when that person is trying to find someone else in you?? The thing is your old friends always fall in the former category... They have already become quite used to your ways, have accepted you just as you are, and the rare times when they give you some suggestions to improve, they are just being your critics...
But the question here is when you are in the process of knowing a new person to be friends... Here comes the difficult dilemma of that person finding it difficult to accept you as you are or providing an objective opinion of a well wisher for your genuine improvement! What do you do in such situation?? Run away from that person or try to see the genuine concern that person has...
But then the next question is that if you choose the latter, how to do it?
May be consulting your old friends is a good idea... Now if your old friends disagree with the opinion of the new friend, then do you think that your old friends are too used to you or do you think your new friend is trying to find someone else in you?? And in case you choose the latter, what do you do??

Confusing... isn't it?? Answers anyone?? I am perplexed :P