The Butterfly Effect

Although the premise was ludicrous, and although Ashton Kutcher was supposed to play a cogitative type of guy (pshah!), it wasn't half bad. The protagonist sacrifices being with the one he loves in order that she and everyone else might be happy - oops, I guess that was spoiler. The one thing I don't understand, though, is when exactly his character decided that he was in love with her, because it was in no obvious before he started travelling through time.