The Shrek Forever After star admitted she was unprepared for the period of "terrible numbness", felt following Emilio Diaz’s death two years ago.
"It's impossible for anyone to know what's it like until it happens to you. It had happened to friends of mine and I'd go, 'Oh, I'm so sorry', but in reality? How could I be truly sorry when I didn't know what it meant?" she told Vogue.
"No one can ever underestimate how devastating it is. But at the same time what I've learnt about losing someone so close is that my life is full of his presence."
Diaz's new movie Knight and Day opens on June 25 in US cinemas.