For eight years, he spent most of his days embodying ruthless, highly strung Hollywood agent Ari Gold, but it was only when he stepped away from the television juggernaut of Entourage that Jeremy Piven realised the toll his iconic character had taken on his health.
Talking to Living about reprising his Golden Globe and Emmy-winning role for the Entourage movie, Piven admits his blood pressure shoots up when he steps into Ari's shoes.
"Without a doubt. I remember trying to go for a run after a day of shooting Ari Gold on the show and my hands were numb and I didn't know what that meant.
"As I get older, I realise that part of how we age is how we deal with stress and I don't know how to fake it - when I act I put everything I have into it. So if my character is having a temper tantrum for 12 hours a day, my system's thinking it's in fighter mode and that can be pretty taxing.
"For eight years I was wreaking havoc on my system - and living the dream creatively, but you don't know how exhausted you are until you get a real break."
If the effects on his body or the prestigious awards weren't testament to how significant Piven made the role, his encounters with Entourage fans continue to cement Ari's legacy.
Viewers frequently speak to the 49-year-old as if he really is the neurotic fast-talking agent - something he sees as both flattering and offensive.
"With the show, a lot of people thought I was improvising my monologues and that's one of my proudest achievements.
"People thought, 'He is that character. He steps on to set and just starts yelling and breaking stuff'.
"The reality is I'm not. I grew up in a theatre family, I have a very serious yoga practice and I'm a calm person. I did a documentary in India searching for the routes of yoga and spirituality and it's a big part of who I am. When people meet me they think I'm stoned and want to know why I'm not screaming and crazy.
"But that's never written about - what's written about is the misperception that I am this self-consumed, loud, abrasive Hollywood type.
"It's surreal because I wasn't able to navigate through the Ari Golds of the world - the sharks. They were too offensive to me, so to be mistaken for one is very odd.
"It used to hurt me then at a certain point you realise none of that's real and the people who know me, know me."
Further puzzling Piven about his sudden notoriety after the series - which chronicled the Hollywood experiences of actor Vince Chase (Adrian Grenier) and his friends and debuted in 2004 - was the time at which he got his biggest break.
With acting in the blood, he had trained at his parents' school, the Piven Theatre Workshop, and to this day Mum Joyce still rehearses with him - "hearing my mother run Turtle's lines is hysterical".
Earning a degree in theatre, Piven then appeared on sitcoms such as The Larry Sanders Show and Ellen and movies including Black Hawk Down and Serendipity.
His career was steadily burgeoning, so when a seemingly bit-part on Entourage came along, he thought twice.
"I was 40 movies into my career before I started Entourage and was told not to do it by everyone in my team because at the time I was getting offers to play leads and produce my own show. Bigger roles with more responsibility - and money.
"But you have to put your ego aside and quiet that side of you telling you what you deserve to be doing and just do the best role.
"Ari Gold was a fringe player - the smallest of all the characters in the Entourage pilot. I had to take a leap of faith knowing that if he was interesting enough, he could grow.
"The big lesson was to not be a slave to your ego and just figure it out because I did have to prove myself all over again. I won the Fresh Face of the Year award at 37 years old. My face was not fresh at all!
"By Hollywood standards, I was a late bloomer."
For males, late-blooming is not uncommon in Hollywood and for Piven the rise continued after the show's 2011 end.
From his most legendary role to perhaps his proudest, he has since been starring in British period drama Mr Selfridge, playing the owner of the prestigious department store.
If it wasn't for his time in Harry Selfridge's shoes, Piven would never have agreed to the Entourage film, in which Ari returns as the head of a studio making a film directed by Vince.
"It's crazy that I will have completed four seasons of another show - I've been cheating on my boys!
"But everything I did with Mr Selfridge and working with some of the best actors in the world informed the work I was able to do in this movie. When you work with actors who have been on stage their entire lives they raise [your] game.
"Ari is an overly emotional, invested character while Harry Selfridge is a pioneer, who leads with love and by example - not with an iron-fist. He's the antithesis of Ari Gold, so I'm challenging myself with this period drama.
"The irony is it's a hit everywhere in the world except my own backyard."
Entourage is screening now.