it's when you hold eye contact for that second too long or maybe the way you laugh. it sets off a flash, and our memories take a picture of who we are at that point when we first know "this is love." and we clutch that picture to our hearts because we expect each other to always be the people in that picture. but people change. people aren't pictures. and you can either take a new picture, or throw the old one away.
"No matter the history with someone, you will always know the one person you want to be with. I sure do, no matter how much my friends and family tell me otherwise. They don't know my mind."