He's completely and utterly in love with you, and there's no escaping from the feelings that run through his body whenever he sees you. There have been many women in Sam Winchester's life. He knows a lot about falling in love, he has seen it and felt it all, or so he believed. His life as a hunter allowed him to have different relationships, some deeper than others. Even so, there has been no one in his life like you. You showed him what he was missing and more. He never thought, for a man like him, that he would find someone he would want to spend the rest of his life with. Everything happened so fast after Sam met you, when he realized he was falling for you, it was too late to fight back. Not that he wanted to. Now he's in too deep, so in love that you have him on his knees. Sam cannot imagine if it ever comes a day when he has to be without you. So, when he shows you the ring, the only thing left is for you to accept him.