Diane Keaton left behind a 'drearier world,' says longtime friend Woody Allen

Allen wrote an essay about the movie star after her death at age 79.

The actor noted the two were both shy but eventually shared lunch together during rehearsal.

"That was our first moment of personal contact," he wrote. "The upshot is that she was so charming, so beautiful, so magical, that I questioned my sanity. I thought: Could I be in love so quickly?"

According to Allen, "only God and Freud might be able to figure out" why they didn't last as a couple.

"A few days ago, the world was a place that included Diane Keaton," he added. "Now it's a world that does not. Hence, it's a drearier world. Still, there are her movies. And her great laugh still echoes in my head."

"She declined very suddenly, which was heartbreaking for everyone who loved her," a friend of Keaton's later told the outlet. "It was so unexpected, especially for someone with such strength and spirit.

"In her final months, she was surrounded only by her closest family, who chose to keep things very private," the insider added. "Even longtime friends weren't fully aware of what was happening."

Allen explained that out of all the opinions, he only took Keaton's thoughts on his films to heart.

"I never read a single review of my work and cared only what Keaton had to say about it," he wrote in The Free Press. "If she liked it, I counted the film as an artistic success. If she was less than enthusiastic, I tried to use her criticism to reedit and come away with something she felt better about."

Fox News Digital's Ashley Hume contributed to this report.