True, it may be a definitely good sign but it also may be a bad one. It all depends under what circumstances you change your mind. If it's because of peer/social pressure - that's not really great. If you listen to one's argument and come to conclusion that they've indeed got a point - it's definitely good to change your mind. I'd even say that not only is this a sign of strength but also wisdom, admitting to your mistakes and accepting others' different views.
Very good point!! :)