Monday's Dancing with the Stars was "Most Memorable Year" Night, and you would think former Malcolm in the Middle star Frankie Muniz would have chosen 2000, the year Malcolm in the Middle shot him to stardom, but instead he chose 2017 for a bittersweet reason: he has suffered memory loss that he suspects is the result of a series of concussions and mini-strokes. So 2017 is the year he learned to stop worrying about what he doesn't remember and start living in the present.

In 2012, Muniz had his first transient ischemic attack — a loss of blood flow to the brain without tissue death — and had another in 2013. He's also had nine concussions throughout his life. He doesn't know for sure that those are what has caused his memory loss, since he's never really talked about it before, not even with doctors. It's affected both long-term memory — he doesn't remember much of Malcolm and the Middle — and short-term. To help him keep track of things, his girlfriend keeps a journal of what they did on any given day, because otherwise he can't pull it up in his mind.

"It makes me a little sad," Muniz said. "Things pop back into my mind [that] I should have remembered."

Tom Bergeron, Witney Carson and Frankie Muniz,<em> Dancing with the Stars</em>Tom Bergeron, Witney Carson and Frankie Muniz, Dancing with the Stars

But he has support, both from his girlfriend Paige and from his Malcolm in the Middle dad Bryan Cranston, who appeared in the pre-taped segment before Muniz's dance.

"I told him not to worry about what you remember and what you don't remember. They're still your experiences," Cranston said. "It'll be my job. I will tell him, 'Remember this? Remember that from Malcolm? What a life for you!'"

"My most memorable year is 2017, because I learned to live in the present," Muniz said in conclusion."I'm happy with my acting career, I'm happy with the decision I made to drive race cars and to focus on music. Even if I don't remember it all, I'm happy."

After the emotional admission, Muniz and his partner Witney Carson did a quickstep to Coldplay's "Adventure of a Lifetime," earning a 24/30 — a respectable showing, especially considering Muniz was dancing with an ankle injury.

Dancing with the Stars airs Mondays at 8/7c on ABC.