Thank you for your letter, and I'm truly sorry Christmas was such a depressing time for you. Christmas shouldn't be this way; it should be a time of joy and peace. But because we are sinners, it often isn't.
The most important truth I can tell you is that although you feel alone and unloved, in reality you aren't -- because God loves you, and He is with you. So far in life, you haven't thought about Him very much; you even might have been angry at Him or not wanted anything to do with Him. But God created you and loves you, and you are of great value to Him.
In fact, if you had been the only person on earth who needed to be saved, God still would have sent His Son into the world to die for you. Jesus Christ is the final proof of God's love for you -- and that's why I urge you to turn to Him in repentance and faith, and welcome Him into your life. The Bible says, "This is love: not that we loved God, but that he loved us and sent his Son as an atoning sacrifice for our sins" (1 John 4:10).
You can't change your family -- at least not now. But you yourself can be changed, by allowing Jesus Christ to have control of your heart and mind. Remember: we are never alone when we know Christ.