While speaking to The New York Times earlier this week, the 31-year-old actor -- who played Neville Longbottom in the "Harry Potter" movie franchise from 2001 to 2011 -- said it's "painful" to watch his performance in the films as he sees "too much" of himself in Neville.
"I find it quite difficult when too much of me starts to come through in a character," Lewis said. "It's easier when I can play someone completely different, like a police officer in London or someone who's wealthy."
"At times it's painful how much of me there is in Neville," he continued. "When I'm watching, I'm like, 'That's not Neville; that's you.'"
David Yates, who directed the final four "Harry Potter" films, explained how Lewis's performance transformed over time.
"Matthew was very much a supporting player when I arrived to direct 'Order of the Phoenix,'" Yates told the Times. "But he became more confident, more curious, more present as the films progressed. And more ambitious."
Yates brought up a scene he wrote for Lewis and his character for the last Harry Potter" film, "Deathly Hallows: Part 2." The sequence, which wasn't featured in the books, shows Neville blowing up a bridge in order to slow down Lord Voldemort's army from entering Hogwarts.
"It captured the charms of Neville and Matthew's everyman quality," Yates said. "He had a modesty and an honesty that was hard to ignore."
Although he might not enjoy re-watching himself in the "Harry Potter" films, Lewis doesn't mind if he'll always be referred to as a "former Harry Potter actor."
"If there's something people remember you by, there are worse things than the Harry Potter franchise," he said. "It opened so many doors for me when I otherwise wouldn't even have gotten in the room."
The actor, however, is being seen in a new light as a romantic lead in a reboot of "All Creatures Great and Small" which you can catch on Masterpiece PBS.