Love is a Promise.
Ever since we were little kids we made dozens upon dozens of promises whether it was in the school yard or in the park or anywhere really. Our friends would always have a secret that they needed to share and they would come to us to have it protected. We would hook our pinkies with theirs and smiling say "I promise"
But it wasn't just the secret you protected by keeping your promises. You also protected your friend. You showed loyalty to them and that your cared deeply about them. So deeply in fact that when asked about the secret by anyone else you'd make a face and tell them to scram.
When you love someone they become your best friend. They become the most important thing to you. Love is your promise to them. By loving someone you promise to cherish and protect them and to always be by their sides. Your promising yourself and everything you have, every feeling you share for that person. Even now you may hook pinkies with someone you care about to make a promise and to show that you love and care about them (I'm sure we've all done it even as teens or adults :P)
To me love is the one promise that should never be broken. Love is the one promise we should always keep dear to us and protect with everything we have because Love is something more powerful than pain and sadness.
Love is beautiful. Love is a Promise.