The British star found success in the mid-2000s after his zombie comedy "Shaun of the Dead" became a huge hit and earned him roles like technology expert Benji Dunn in "Mission: Impossible III".
However, behind the scenes the actor was battling an alcohol problem and attended the Priory Clinic before starting work on the next "Mission: Impossible" film, 2011's "Ghost Protocol".
Speaking to British newspaper The Sunday Times, the star explained that filming the movie helped him quit booze for good, as he praised the production team for being "really helpful" and supporting him on his journey to sobriety.
"They made sure that my family was on standby to come out if needs be," he shared. "One of the problems you have as an actor sometimes is separation anxiety. You're away from your family a lot. I'd just had a baby and the thought of being away for a long time was troubling me, so they were just really helpful in making sure I was feeling happy and comfortable."
Crediting director Brad Bird and co-star Tom Cruise with helping him recover, he added, "By that time I was in a much, much better place. That film couldn't have come at a better time because I got in good shape and started to just have fun, working with Brad and Tom. It was an adventure. We went to Prague and Dubai and Vancouver. It was part of my recovery, I think."
Speaking of Tom's help on set, he explained, "I didn't ask who knew (about his alcoholism), but I think he did. He's always been very supportive."
While Simon is convinced his co-stars knew of his problematic relationship with drink, he confessed he struggled to tell close pal and comedy partner Nick Frost about it.
"I think Nick knew, but he didn't want to admit it because it was too scary," Simon says. "But it's a very private hell that you're in. You're trying to look OK to other people."
"You're creating this reality that you're not unwell, and you're trying to believe that, whereas really you're clearly not well and you're very sad, and drinking, or whatever you're doing, to try and change how you feel. It's a strange kind of split personality that you have."