In her new memoir, "The Woman In Me," Britney recalls the interaction, writing ... "It had been a while since I'd seen him. Everything was going great in his world. He was at the top of his game in every way, and he had a lot of swagger. I was having a panic attack."
Britney says she "hated the way I looked" ... because "It was less than a year since I'd had my second baby in two years but everyone was acting like my not having six-pack abs was offensive."
What's more, Britney admits she hadn't rehearsed enough and knew the performance "was going to be bad." She says "nothing was going right" backstage ... claiming there were problems with her costume and hair extensions. She says she didn't sleep the night before, and was feeling dizzy.