In "The Big Bang Theory" Season 7 Finale, Sheldon decided to board a train and leave Pasadena, as he felt he has reached his breaking point. The lure of going to Lego land also did not make him go back to his apartment, with Leonard and Penny.
"Leonard, I'm overwhelmed. Everything is changing and its simply too much. I need to get away and think," Sheldon said to Leonard in the episode.
[Youtube/The Big Bang Theory]
Sheldon arrived at the platform after his University did not let him change his research field, Leonard and Penny got engaged and decided to move-in but without Sheldon, Amy said that she can move-in with Sheldon, and Stuart's comic book store burned down. All these changes were too much for Sheldon to handle. Penny realised that it is important for Sheldon to discover himself and convinced Leonard to let Sheldon go.
Talking about what was the goal of the final episode, Steve Molaro, executive producer of "The Big Bang Theory," said to Entertainment Radio that it was to "chip away at Sheldon and break him down to the point where he just needed to leave to process everything."
When asked about how much the Sheldon's character can change, will it be subtle or it will be big, Molaro said, "If you look at the history of the show over the past seven years, they've all changed quite a bit. Its a slow change, that is how we like to do it. Everybody has really grown, Sheldon, Penny, Leonard..."
Molaro said that everyone is making growth in their own way. He talked about how Howard was a sex pound dog and now he is a married man. He also mentioned how Raj can now speak to women and is dating a girl, successfully. In the season finale, Raj kissed and had sex with Emily.
"Our goal is usually to have the characters grow, but still let them be the characters. There's a line to walk," Molaro said.
Molaro revealed that the writing team has yet to begin writing the new season.