Second of all - I always heard "they're just girls" meaning she's just a girl, not a woman, i.e. very young (he does say "eyes bright", meaning young and naive).
I guess the song is him saying he was hooking up with a young girl, but she, being young, took it as a relationship instead of just a hookup. He starts to get annoyed with her because she's clingy and she's acting like he's what she was looking for. But he realizes that she's just a young girl, and he needs to break it off.
First of all - weirdly obsessed with this song.
Second of all - I always heard "they're just girls" meaning she's just a girl, not a woman, i.e. very young (he does say "eyes bright", meaning young and naive).
I guess the song is him saying he was hooking up with a young girl, but she, being young, took it as a relationship instead of just a hookup. He starts to get annoyed with her because she's clingy and she's acting like he's what she was looking for. But he realizes that she's just a young girl, and he needs to break it off.