This might sound really morbid, but there are only two options for a relationship when it comes down to it.
Either you can (a) live happily ever after with the ring and the white dress and the church bells and all that jazz - and let's be real, most relationships probably don't lead to marriage, since most people don't marry their first boyfriend, or (b) you break up. It may not be today, it may not be tomorrow, it may not even be this year. But chances are that it'll happen and, when it does, there will be heartbreak, tears, woe, and lots of Simple Plan/Good Charlotte/The Red Jumpsuit Apparatus/other angsty music.
Yes, I've had a kicka** breakup playlist since before I even had a boyfriend. Don't hate. I'm prepared.