The 31-year-old actor shot to fame playing Ron Weasley in the wizarding saga when he was just 10 years old, and throughout his time in the franchise, he never thought about the fact it would draw to a close one day.
He said: "Then suddenly it did, and we were out in the big wide world. Which was quite daunting."
Explaining how he felt liberated, he told the Daily Telegraph newspaper: "Like, I had control of my hair again - not that I've ever done anything different with it.
"But something that was really symbolic was I had my tonsils out. I was never able to while we filmed, because of the recovery time, so that felt big."
He didn't think about the fact he had the eyes of the world on him until several years into the franchise, and he's thankful he and his young co-stars, including Daniel Radcliffe and Emma Watson, were "well protected".
He said: "I don't think that really hit me until midway through, when I became a teenager.
"I went through a stage of feeling a bit hemmed in. The fame thing was a tricky thing to understand, being shy, so to suddenly not have that invisibility was a lot to take on.
"There's this classic child actor thing where people are waiting for you to go off the rails. I felt there was a thirst to see that happen.
"But it was a bubble, and we were very well protected. Some days were worse than others, but for the most part it was a great experience."
Rupert - who is in a relationship with actress Georgia Groome - has an estimated wealth of £25 million (S$44 million) but admitted he has a "strange" relationship with money because he's never had to struggle as a result of finding career success so young.
He said: "It's a nice security and I appreciate it, but I have a strange relationship with money because it's always just... been there, in the background, from such a young age.
"I'm very lucky, but it can also make you sit back on your laurels, which I did for a period. But in the last few years I've found a bit of drive."