I often find when I write certain characters that they resemble me more than other. And when I think about their actions, I think about them from my point of view and my experiences. They are acting or saying a certain thing because that is how I would do it. That’s how I realise that the character has lost his or her individuality. They are simply me in disguise. Re-write!
There will always be certain characteristics of mine that shine through, but they still need to have their own thoughts and actions. It is up to me to avoid getting lazy and simply use my own experience. Since I am not writing about my life, the characters should not act in that way. It is a slippery slope to travel down, very soon the book I am writing is about me and no longer a fictional tale.