The esteemed actor recently talked to W magazine
about his role as couturier Reynolds Woodcock in the forthcoming film "Phantom Thread," directed by Paul Thomas Anderson.
Day-Lewis got so into character that he learned to sew -- apprenticing for months under the head of the costume department at the New York City Ballet -- and even recreated a Balenciaga sheath dress using his wife, filmmaker Rebecca Miller, as his model.
But the 60 year-old actor said diving into the life of Woodcock and all the drama it entailed also sunk him into a depression.
"Before making the film, I didn't know I was going to stop acting," he said. "I do know that Paul and I laughed a lot before we made the movie. And then we stopped laughing because we were both overwhelmed by a sense of sadness."
According to the actor, it was a revelation.
"That took us by surprise: We didn't realize what we had given birth to," he said. "It was hard to live with. And still is."
In June, Day-Lewis, who has won three Academy Awards for best actor, shocked fans when he released a statement announcing he was retiring.
He told the publication he's not entirely sure why he feels like he needs to quit now.
"But it's settled on me, and it's just there," Day-Lewis added.
The actor isn't even planning to see the film that may have ended his highly lauded career.
"Not wanting to see the film is connected to the decision I've made to stop working as an actor," Day-Lewis said. "But it's not why the sadness came to stay. That happened during the telling of the story, and I don't really know why."
He said he went public with his decision as a way of drawing a line.
"I didn't want to get sucked back into another project," the star told W. "All my life, I've mouthed off about how I should stop acting, and I don't know why it was different this time, but the impulse to quit took root in me, and that became a compulsion. It was something I had to do."
"Phantom Thread" comes out in theaters on Christmas Day.