In 'The Let Them Theory,' Mel Robbins charts a path forward to release what you can't change — and seize what you can.

Mel Robbins, author of ‘The Let Them Theory,’ greeted fans at an event in Boston in January. Photo: Erin Clark/Boston Globe/Getty Images. By . Jeffrey A. Trachtenberg. and .

Joining the trio is iconic singer, songwriter Mel B, who was on the series from Seasons 8-13. “Last time I was on the judging panel, I was in a very different place,” explained Mel B.

Mel B celebrates her teenager Angel's 18th birthday, saying she "couldn't be prouder of watching you grow." The singer shares her child with ex Eddie Murphy.