Peter Dinklage was "a bit of a mess" as a young actor.
The 52-year-old star admits that in contrast to some of his younger co-stars, he lacked focus early in his career.
He said: "I’m always taken aback by these very professional young people in my business who seem to have it all figured out.
"I was a bit of a mess. I spent too much time thinking I was Jack Kerouac but not writing like Jack Kerouac. I guess in your twenties you’re supposed to be doing that, working out what you don’t want to do any more - like smoking - but making a lot of mistakes and learning from them. I got more serious in my late twenties."
Peter played the part of Tyrion Lannister in the HBO series 'Game of Thrones', and he admits that the high-profile role changed his life and his career.
He told The Independent: "['Thrones' success] does afford you the luxury of being able to be more particular about what you do.
"There are jobs you take, and maybe later wish you hadn’t, but no regrets, it’s work, and we’re all lucky to be working."
Peter has a form of dwarfism known as achondroplasia - but he won't allow it to define who he is or his acting career.
Peter - who has also starred in 'Three Billboards Outside Ebbing, Missouri' and 'X-Men: Days of Future Past' - explained: "I read a lot of scripts where the height is the only characteristic of the character, but that’s not who I am. It’s part of who I am, but I don’t go around thinking about it all day long. And if it doesn’t define me, why should it define a character? That’s just bad writing."