Ahhhh, romance...
Kisses, hugs, cuddles... flowers for no reason at all...the old-fashioned "down-on-one-knee" proposal...
Knowing even if you fight, you'll make up. That you can and are willing to compromise. Knowing someone well enough to know that there are things you aren't going to see eye-to-eye on, but you respect the other person enough to try and come to an agreement.
Being able to trust that your special someone will be true to you, being able to have an unwavering faith that even if they occasionally look at someone else that it's out of a general appreciation for beauty and not because they are looking to stray.
Honesty, even if it hurts sometimes. Loyalty, even when times are difficult. A deep-seated knowing that you are willing to fight for what you've got.