Katy Perry - Katy Perry Was Exhausted Before Big Brazil Show

The Firework singer admits she almost walked away from the Rio de Janeiro show last year (11) because she didn't think she could perform at her best - and her new concert movie Part of Me features footage of her battling emotions and exhaustion in the days before the gig.

She says, "Right before Brazil was a very difficult moment. I was, like, so exhausted. I'd been flying around the world.

"You see... me not knowing whether I should go onstage, but it's, like, the biggest show of my whole tour; it was, like, over 20,000 people, so I couldn't let them down - and all their babysitters."