" 'Do not mess this up everything will come crashing down if you mess it up,' " Swift said. "It's a little more intense and the voice is a little meaner, but that's basically what happens."
Ooh. Is she going to shout?
I think she means that the voice in her head that says that to her is meaner and more intense.
Swift has single-handedly converted a lot of pop music lovers to country music since she has become one of the most influential artists of her generation.
I wouldn't have known and appreciated this genre if not for her.
when SN crosses it ...! 
would be #7 without them! 