Rupert, who is now 30, says that he can't watch past the third movie - Harry Potter and the Prisoner of Azkaban - and that he "struggles to remember life" pre-HP.
In an interview with the Radio Times, he said: "I think those early ones are OK. More time has passed. I can detach myself a bit more from that kid.
"I did see Harry Potter and the Philosopher's Stone not long ago, for the first time since the premiere, and I actually enjoyed looking back.
"But the more recent ones I definitely couldn't do."
When he was asked about which is the latest film he could watch, he said: "I could probably go up to Harry Potter and the Prisoner of Azkaban."
Rupert was only 10 when he landed the amazing role of Ron, alongside co-stars Daniel Radcliffe (Harry Potter) and Emma Watson (Hermione Granger), and it was overnight that they became mega-stars.
"I struggle to remember life before it," Rupert explained. "I think I lost myself a little bit along the way. With the fame, you're almost being the character even when you're not in character.
"From the moment I got the part, my life completely changed. It was a weird time and it has taken me a long while to process.
"Just being invisible can still be difficult. Sometimes you just want to go to B&Q."
After the movies were over in 2011, Rupert also struggled to know what he wanted to do.
"I had this feeling that I had missed out on normal things," he added. "I lost touch with a lot of my friends from school. I wanted to have a bit of a life again, so I took a break."
Now, Rupert still acts.
He recently has starred in BBC's The ABC Murders, as Inspector Crome - a role that earned him rave reviews from critics and viewers and one that he said he thoroughly enjoyed doing.
He explained how he enjoys playing "someone with authority" as opposed to the "vulnerable, nerdy sidekick".
Ouch, our hearts.