ICYMI -- ADR had been in the news for other reasons over the past year -- he had a very public breakup with Paige and was investigated for domestic violence after an airport incident (he was cleared of any wrongdoing).
Alberto says he's been humbled by those incidents ... and that's what got him back in the gym training like a madman.
"For the first time after 19 years, I started doing some sparring with my boxing coach, with my jiu-jitsu coach and I was like, 'damn, I think I can do this again.'"
Del Rio says he even questioned if he'd be able to compete on a professional level again ... but he's not giving up for good reason.
"I’m doing this for the right reasons, to prove something to myself. To prove me that I’m back. To prove me that I still have it. To prove to my children that Dad is a f***ing superhero!!"