what do you say......

so three of my friends from high school are going to Iraq this fall. i really don't know how to react. i guess this is the first time that i've really come to reality that there is a war going on. i'm so used to reading about wars in textbooks but now it's real life with my real friends going to the frontlines. i've experienced wierd emotions that i've never felt before. when i said goodbye to one of them yesterday i got teary eyed and said "good luck". is that what you're supposed to say? do you say "hope to see you soon" or "have fun" or what?