John Cena has had his share of struggles.

The 40-year-old WWE star is opening up about being bullied as a kid, and how that helped him find his passion for wrestling.

Related: John Cena Teams Up With Crocs Campaign to Stand Up Against Bullying

Cena recently teamed up with a footwear brand in order to encourage people to embrace their differences. In an interview with CBS News, he says that the reason he wanted to be part of the campaign was, "to showcase not only my childhood past and what got me into the realm of physical fitness, which eventually led me to define myself, but also the current state of affairs."

The athlete, who is engaged to Total Divas star Nikki Bella, added that he's had to endure a lot of criticism throughout his career. While many might look at his life and say, "everything's great," he shares that "there's a lot of struggle involved, and I'm...