Jim Parsons is opening up about his decision to leave “The Big Bang Theory”.

The Golden Globe winner, 46, has starred as the beloved Sheldon Cooper on the hit comedy series for 12 seasons, and late last year he revealed he was stepping away from the show.

With the series finale airing on Thursday, Parsons chatted with The Hollywood Reporter and finally revealed why he decided to exit.

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“It was the first time in my life of doing this show that it occurred to me that I might want to not do another contract after 12 was up,” Parsons said. “I don’t know if it’s because I’m an Aries or just because maybe I’m in touch with myself. Whatever it is, once I had that thought, I was like, well, that’s your answer.”

He added: “There was no factor; there was no situation that I was like, well I’ve had enough of that. No. There was nothing like that. It as just… when you know, you know. And you’re susceptible and thrown around by the whims of your own existence and getting to a certain age and your life changes and suddenly you just think different. It has been fascinating to think about who I was 12 years ago. And sometimes when I have trouble learning a line or saying a line of Sheldon’s right now, it’s hard to know why specifically.”

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And since the start of the show, Parsons married Todd Spiewak, “It’s like, you’re not the same person you were,” he said. “There is a possibility that this actually became more difficult for you in a way. And I don’t know what that means but it’s like you just change.”

According to series creator Chuck Lorre, continuing the show without Parsons onboard. “I couldn’t wrap my head around the idea of going on without the whole ensemble,” he told THR. “In pulling it apart and re-approaching it as a fraction of what it was just never felt right to me. I’ve seen other shows try and fail to take a character out of their realm and carry on.”

The series finale will air Thursday, followed by a half-hour special called “Unraveling the Mystery: A Big Bang Farewell,” hosted by “BBT” stars Johnny Galecki and Kaley Cuoco.