"Personally, it affected me in ways I can't necessarily put in words or even would want to talk about publicly."
Jake Gyllenhaal has spoken frankly for the first time about the tragic death of his one-time co-star and close friend, Heath Ledger.
Heath died eight years ago at the age of 28 after accidentally overdosing on prescription drugs. (He would have turned 37 this week on April 4.)
The tragedy occurred only a few years after Heath and Jake starred together in Brokeback Mountain, for which they both received their first Oscar nominations.
Today, Jake, 36, told PEOPLE how Heath's death affected him personally and professionally.
"Personally, it affected me in ways I can't necessarily put in words or even would want to talk about publicly," he said.
"In terms of professionally, I think I was at an age where mortality was not always clear to me."
Brokeback Mountain, 2005.
In particular, Jake confessed that Heath's death really made him look at fame and his own mortality in a whole different way.
"I think you live in this bubble, too, of making films. There are real friends, and there is a real community... but There is also that [new Macklemore song] where he says, 'The curtain closes and nobody notices'. I think that's true, and I think that's okay," Jake said, reflecting on fame and the film industry.
"But I think at the time, I assumed everyone would notice – and they did with Heath dying, but I think it [gave me] the experience of, 'This is fleeting.' And none of the attention or synthesized love that comes from the success of a film really matters at all.
"What matters is the relationships you make when you make a film, and the people you learn from when you're preparing for a film. That changed a lot for me."
Jake is the godfather of Heath's daughter, Matilda.
He remains close with Heath's former partner and Matilda's mum, Michelle Williams. All three appeared in Brokeback Mountain together in 2005.