Can you change who you are at your core?

If you want to reconnect with your old friends, then do it. Sometimes we just loose touch with people, there is nothing wrong with reconnecting with them on face book, that is what those sites are for. You are not a bad friend because you are an introvert, don't let other people get you down like that. Nothing is stopping you from reaching out to your old friends, they would love to hear from you, especially since it is the holidays. Don't change who you are, be yourself, chase your own dreams.