Does anyone know any songs about wanting to be in a relationship that might not work?

I have been seeing this guy for a couple months now, we are starting to get serious and I really want to be with him, but I joined the Army maybe a week before we met, so I will not be around for almost a year. It will be difficult to form a relationship since we only have 2 months until I leave. I am really starting to fall for him so my heart is starting to break.. does anyone have any songs for this? I honestly will accept any genre.. I am very eclectic in my musical tastes. =] thank you guys