Heath Ledger’s untimely death was a blow to movie audiences everywhere, who would miss out on future performances from a truly talented actor. Imagine, then, how that loss was magnified for those, like Brokeback Mountain co-star Jake Gyllenhaal, who knew Ledger on a more intimate level.

"Personally, it affected me in ways I can't necessarily put in words or even would want to talk about publicly,” Gyllenhaal told PEOPLE's editorial director Jess Cagle of Ledger’s death. “But in terms of professionally, I think I was at an age where mortality was not always that clear to me.”

Gyllenhaal, who was 27 at the time of Ledger's passing, says he hadn’t yet suffered many losses, and that Ledger's death ultimately altered his perspective on life and the things he deems most important.

"I think you live in this bubble, too, of making films...There are real friends, and there is a real community," he said. "But there also is that Macklemore new album where he says, 'The curtain closes and nobody notices' and I do think that's true, and I think that's okay.

"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,’” he continued. "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."

Watch Jake Gyllenhaal discuss Heath Ledger's death in the video above.

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