When he's your best friend for so long and you think that he's just your friends while you treat him differently (maybe because don't know what's love). And one day he tells you that he's in love with someone. You don't hear anything, it's like time has stopped and you've lost your breath, like whole world is against you now. And you realise that you're in love and maybe you were in love but you thought it was a friendship. You understand that this is your first and last innocent love, which isn't mutual. You understand that you should move away from him, because he will still continue to talk to you as a friend, although he could spend time with his love, who makes him happy. Although at the beginning you support him and talk to both like to romeo and Julie and pretend exited. You just know that you can't continue like this. You start pretending to be a different person, acting stupid, talking less to him to make him angry and hate you. Because it's the best way to make if look like your friendship ended Because of your behaviour not because of your love, so he won't know anything about your feelings. You feel happy for him even when he loves another person because you love him and you want all the best for him. I don't really understand what I wrote but I hope you get it. I think you're truly in love when you're happy for him even if his happiness isn't you or not related you. You're just happy, because he's like your backbone