"I needed to make a change because I was tired of the way I was living."
That's 31-year-old former heavyweight champion Andy Ruizopening up about depression that literally brought him to his knees ... after losing his belts to Anthony Joshua.
TMZ Sports talked to Ruiz days before he makes his return to the squared circle on May 1 ... where "The Destroyer" will take on Chris Arreola.
When Ruiz starts letting his hands fly ... he'll look a little bit different than the last time we saw him in the ring with Joshua -- 'cause the 6'2" boxing star has lost nearly 60 pounds!!
"I think the weight loss is gonna be good and gonna be an advantage for me," Ruiz tells us.
"I think I'm gonna be a little faster, I'm gonna be able to slip more punches, bob and weave and things that we've been practicing in the gym and you know, I'm still not where I wanna be at but I'm still way better than I was before."
Of course, Ruiz SHOCKED the world and KO'd AJ in June 2019 ... one of the biggest upsets in heavyweight boxing history.
But, the December 2019 rematch didn't go nearly as well for Ruiz ... who stepped into the ring weighing 284 pounds, and looking out of shape in a unanimous decision loss.
After the fight, Andy says he was depressed and knew he had to change his life ... and that started with the drastic weight loss.
"There was just this one day that I was just depressed with myself and I was weighting 310 lbs. I thought losing weight would be the big issue and learning discipline, because I lacked discipline in my whole professional career," Ruiz says.
Andy continued ... "Like I said, I was depressed, I had got on my knees, I started praying and started telling God for a new change, a new mentality, and the next day I woke up and I woke up like a brand new man and that's when I messaged Canelo and told him if he could open the doors for me, and here we are now."
If the new, improved Ruiz beats Arreola (and he's a massive favorite) ... Andy could potentially face Deontay Wilder, Tyson Fury, Dillian Whyte or even Joshua for a third time.