Hello, my dear (Имя друга) !
I haven't ssen you for many months. How are you? What's new? What are your plans for christmas and new year?
I am going to spend my winter holidays with my family and relatives at home. I am sure that we wiil have a good time. I will be waiting for you very much! Our company without you is almost empty. Greetings to your family, especialy to your sister Sarah.
Hope you will come!
Best wishes, (Твое имя).