Sharon said:
“Epic was written in the aftermath of a really bad relationship. This guy didn’t even let me have a guitar. I don’t have any bitterness toward him because he kicked my ass into leaving Tennessee. But the record isn’t about him; it’s about me getting over that situation.”

SPIN Magazine

You can hear her explain the song and see the recording process in this video:

https://youtu.be/rIdIHO9qVbg