Like this line in the song says "I see the way you're actin like you're somebody else." Also she say's "You tryin to be cool but you look like a fool to me". I think if you listen to this song you should really think about what she's saying.
The songs not saying you can't fool around once in a while but don't just change your image to get people to like you. After all don't your friends like you for who you are?
This is a really good song for people who don't think they're hurting anybody when they don't act like themself. The truth is they're really hurting themself. They're hurting themselves because the friends they had that originally liked them will probably think they are acting dumb.
The point of the song is more than just be yourself, it's also about just like yourself the way you are and just be happy with the friends you have because they like you for who you are not who you pretend to be.