She shared heartbreak with sister Bronte when they came sixth and fourth respectively in the freestyle race.
The New Daily are reporting Campbell acknowledged that her strong swims in the lead up to the final were a major reason she let her head get ahead of her preparation.
Campbell broke two Olympic records in just two swims in her two races before the final on Thursday, meaning she was an overwhelming favourite going in to the final.
“I just spent too much emotional energy in the lead-up,” she said.
“I let my head get ahead of me. It’s not something I should do.
“It’s hard when you are in form coming into an event not to think about outcomes,” she added.
The Australian swimming team's Head Coach, Jacco Verhaeren, also conceded he believed one of the stars of their team was wracked by nerves.