But he's clearly found a rhythm with Clint Eastwood, whom he views as a mentor despite Hereafter only being their second film together.
"I hope this is the second of 10 movies with Clint. He didn't even have to give me such a wonderful script.
Maybe I'm gonna freak out or something, but it hasn't happened yet," he says, smiling good-naturedly, looking today like he's stepped from the pages of a preppy men's fashion catalogue with his cashmere sweater, jeans and spectacles.
Just 26 years old when he and writing partner and co-star Ben Affleck took home the Best Original Screenplay Oscar for Good Will Hunting, the childhood best friends were bursting with promise.
Exchanging bachelorhood for his present-day status as father-of-four within just eight short years has certainly caused him to contemplate the meaning of life and death more than he would have otherwise.
"I think having children adds a whole other layer of where you start thinking a little deeper about your mortality," says the actor, who recently turned 40, indicating his prematurely-greying hair. I always say to them – this [grey hair] is all you and this side here is you! "Clint makes the other side of the hill look pretty appealing.
I was doing an interview for Invictus a year ago with Morgan [Freeman] and when somebody mentioned I was going to be 40, Morgan said that I was coming into the best two decades of my life.
It was a potential that could have led them anywhere – or, most likely scenario, that just one of the dynamic duo would succeed.
But the movie gods were shining on them both, each going on to enjoy great success, Affleck recently receiving much acclaim for The Town, a film he directed, wrote and starred in.
Starring as a psychic who sees dead people in Clint Eastwood's Hereafter forced Matt Damon to question whether or not there's an afterlife."I'm hopeful. Maybe the light does just goes off," he says today.
"But we'll all find out sooner or later, that's for sure." Wed five years to Argentinian-born barmaid Luciana Barroso, Damon became an instant dad to her daughter Alexia, now 12, and together the couple are now also parents to girls Isabella, four; Gia, two, and three-month-old Stella.
Or, as Affleck put it a few months ago while attending the Toronto Film Festival: "It's pretty amazing that we're both here. It's actually quite mind-blowing." Damon isn't any less humbled by his success.He's actively involved in charitable work, including the ONE Campaign and grateful for a career in which he's starred in such critically acclaimed films as Saving Private Ryan, Syriana, The Informant and The Departed as well as box-office pleasers like The Bourne trilogy and Ocean's Eleven, Twelve and Thirteen.