The original form is the contagion of fear and alarm. You're in a flock of birds. One bird suddenly takes off. You have no time to wait and see what's going on. You take off, too. Otherwise, you're lunch.
Deep inside, she knew who she was, and that person was smart and kind and often even funny, but somehow her personality always got lost somewhere between her heart and her mouth, and she found herself saying the wrong thing or, more often, nothing at all.