Despite starring in several big movies such as 'Warrior' and 'The Great Gatsby', the 40-year-old actor often worries he will make a mistake on a movie during the early stages of filming or thinks the director might realise he's made a mistake casting the star in the motion picture.
He said: "The first few days are so nerve-racking for me. The anxiety, trying to block out whether or not I'm going to get fired, thinking I don't know how I'm going to do this, how are they going to feel about that?
"And maybe I'm not the right person ... it's like being at school, arriving first day and having all the kids stare at you."
Despite his nervousness on set, Joel admits he enjoys his profession because he gets to meet so many stars of the film industry and he is glad every big-name star he's met so far has been nice.
He explained: "Being an actor is a blessing and a curse. You get to meet a lot of people you've been watching for years.
"You get to meet Ridley Scott and Christian Bale, people I admire.
"You think, 'God, I hope they're going to be nice people,' and they are. They didn't come down a rung at all in my mind."
The Australian actor loves to travel around the world in his spare time but sometimes finds himself moaning about being in big cities.
He added to Metro newspaper: "I find a reason to complain about anything.
"I caught myself complaining about being in Paris the other day. My brother calls it A-Class Problems."