This is coming from how you experienced your childhood, perhaps you were abandoned or had a parent that failed to provide you with any true nurturing and caring. Instead you learned that you had to "pretend" to be for your parent and for others. It's always sad to see how this develops in someone. Sad, you were only as good as your parent allowed you to be. That's why you are alone, it's only what you know that comes from your past. True compassion and companionship terrifies you because it's so alien to you, and that's sad.