How do you deal with someone leaving?

A good friend of mine is in the Army. He left today for eleven weeks for training. Then he is off to Iraq for God only knows how long. No less then a year and then possibly another two years for another assignment. While on training he cannot have any contact with anyone. I totally understand that, but not knowing when I will see him again is what I am having trouble with. How do you deal with something like this? I know my life has to go on and I can’t sit around the phone and wait for him to call. Any suggestions?