It's basically like saying "WHEW!" because you have finally gotten the piece of paper that makes it official. You know where you're going, but you can't do anything about it until you get your orders. Getting those orders, finally, is a big deal! Standard deal---when you FINALLY get those orders---is to tape a copy on your door/bunk/etc after writing, with a magic marker, in giant letters "FIGMO" across the top.