Jim Parsons has offered The Big Bang Theory fans a window into his decision to quit the show in 2018. And, sadly, the story is not without heartbreak.

Parsons portrayed "Sheldon Cooper" on Big Bang from 2007 to 2019, but it was his exit that brought an end to the popular sitcom after season 12. Today, the actor opened up about what motivated him to move on while appearing on David Tennant's podcast.

Why Jim Parsons quit The Big Bang Theory

On Parsons's episode of David Tennant Does a Podcast with..., he first recalled the uncertainty of Big Bang's future when he signed what became his final contract. "I kind of had a suspicion in my heart that that was going to be it for me when I did sign that contract," he revealed.

Parsons referenced "other things" he wanted to focus on, but he emphasized the mental toll brought on at the time by the failing health of his beloved pet dog. "I was exhausted," he continued. "I was really upset about—more than anything—one of our dogs was getting really at the end of his life around then."

"It was the scariest moment for the next couple of days because I felt like I was at the edge of a cliff. I was teetering and I saw something really dark below between the death of the dog."

Jim Parsons and husband Todd Spiewak's cherished pet dog

Parsons further shared with Tennant the special place of the pet in his relationship with husband Todd Spiewak. "The bottom line was that it was a really intense summer.

"The dog passing away, he was 14, and Todd and I had been together for 15 years at that point, so it just was the end of an era," he recalled.

It's a heartbreaking reveal for Parsons, but he appears not to regret the decision. "I had this moment of clarity that I think you're very fortunate to get in a lot of ways, of going 'Don't keep speeding by.' You know? 'Use this time to take a look around.' And I did," he said.

In May 2020, Big Bang production designer John Shaffner additionally shed light on what Parsons's exit meant to the show. His behind-the-scenes reveal said that the sitcom concluded two seasons earlier than planned as a result of the actor's decision to quit.

'The Big Bang Theory' quiz true or false game trivia questions TBBT cast TV show series sitcom

Quiz

Mayim Bialik ("Amy Farrah Fowler") used to star in the sitcom 'Roseanne'.