How do I deal with the deployment of a loved one?

My boyfriend and I are both seniors in High School. However, he is in the Army National Guard. About 2 weeks after we graduate, he ships off to BCT (Basic Combat Training) for 4 months. He already got warning orders for his unit to be sent to Afghanistan, but there is only a VERY slight chance that he may not be deployed. Since he is infantry, his unit is more then likely going to be deployed in January 2010 for about a year. I've already tried talking to him about all this, but he just keeps saying, "We'll deal with this issue when the time comes." I think about it everyday and it makes me really sad. I really don't know what to do or how to feel. I don't know how do deal with this situation. Any advice is much appreciated! Thank you everyone.