Pharrell Williams says writing 'Happy' broke him. It went on to become one of the biggest songs of the 2010s.

• Pharrell Williams told Zane Lowe's Apple Music interview series that writing "Happy" broke him.
• Williams said writing "Happy" for "Despicable Me 2" came from a place of sarcasm.
• He said the song's success made him realize his insignificance in the universe.

Pharrell Williams ' said "Happy" — one of the biggest hits of the 2010s — "broke" his worldview.

Williams wrote " Happy " for the soundtrack of 2013's "Despicable Me 2," the third biggest movie of the year. Four months after the film's premiere, he released it as a single alongside a 24-hour-long music video.

The song wasn't an instant success in 2013, but it was nominated for an Oscar, won a Grammy for best music video, and topped the Billboard Hot 100 for 10 weeks in 2014.

Billboard marked "Happy" as the best-selling song of 2014 and 21st on its 2010 decade-end chart.

Williams said on Thursday's episode of Zane Lowe's Apple Music interview series that writing "Happy," "Get Lucky," and "Blurred Lines" were defining moments in his career because they were all hits that he was commissioned to write.

He said the songs made him realize he wasn't in control of his success.

"You didn't wake up one morning and decide you were going to make a song about an emotion," Williams said, referring "Happy."

Williams said that he wrote nine songs for the scene in "Despicable Me 2" where Gru is on top of the world after a first date, but his ideas was rejected.

"It was only until you were out of ideas, and you asked yourself a rhetorical question, and you came back with a sarcastic answer, and that's what 'Happy' was," Williams said. "How do you make a song about a person that's so happy that nothing can bring them down? And I sarcastically answered it and put music to it, and that sarcasm became the song, and that broke me."

Williams said the song's success opened his eyes to his insignificance in the universe.

"It's so crazy for us to think like as individuals, everything comes from us. Your ideas, everything that you get, is coming from a library of existence. Nothing is new under the sun," Williams said, adding that he credits the universe for the success of " Get Lucky " and "Blurred Lines" too.

Both singles were some of the best-selling songs of 2013, with "Blurred Lines" coming second on Billboard's year-end chart.