The 23-year-old performed her single at last month's Brit Awards and hinted that it was easy to channel the emotion knowing Styles was in the audience, reported Contactmusic.
"You're balancing the analytical side of your brain, which is telling you where to go and how to go there, with the other side of your brain, which is saying, 'Feel everything you're singing, and show it on your face. Feel everything exactly as you felt it when you wrote the song'," Swift said.