How do I not be sad that Christmas is over?

I had a good time, but now I am depressed because My grandparents and my cuzins Have left. I feel like I will never see them again or I will not see them for a long time because they live far away. Plus, I have to go back to school soon and I still have an essay and a math packet to do. I hate school and I dread coming back to it. I absolutely love Christmas commercials before and during Christmas time, but now that Christmas is over, seeing Christmas commercials is kinda cheesy, and it reminds me that Christmas is over. Also, the Christmas tree is wilted and the ornaments are falling off. I am afraid that the world really will end in 2012, and I only have one Christmas left now before the end. I may not even see my extended family next Christmas! I am just really depressed right now. :( Who feels the same way? How can I feel better?