Or it could be about a girl who he went out with and maybe they went through a nasty break up, and he still loves her. And essentially she broke his heart, and when he finally gains to courage to try and get her back he witnesses her with her new boy and sees how happy she is.
'I guess you're happy because I recognize that smile from better days'
Now he regrets ever letting her go, and is jealous of the boy who has her now.
'And when he's kissing you just like I always used to I hope it kills you knowing what you did to me. He put the moves on you but you will break him too the same as the last one'
I think it could be about cheating.
Or it could be about a girl who he went out with and maybe they went through a nasty break up, and he still loves her. And essentially she broke his heart, and when he finally gains to courage to try and get her back he witnesses her with her new boy and sees how happy she is.
'I guess you're happy because I recognize that smile from better days'
Now he regrets ever letting her go, and is jealous of the boy who has her now.
'And when he's kissing you just like I always used to I hope it kills you knowing what you did to me. He put the moves on you but you will break him too the same as the last one'