"Baby don't hurt me, don't hurt me no more."
Sorry, couldn't resist that :D
Anyway, on the more serious note - to me, love is about knowing that your significant other is there for you, just you are there for them. It's knowing that you will have to deal with them leaving dirty socks on the floor, and them knowing they will trip over your bazilion of shoes on their way out. It's knowing that even if you belong to each other, you are still your own people, who just chose to be with each other and intend to keep that promise, even if the cost can be high at times.