The actor, who played Jon Snow on the show, appeared to break down as he realised his character kills his TV lover Daenerys Targaryen during a read through of the final episode in the TV documentary "The Last Watch", which aired on Sunday night (May 26) - a week after the series ended - and it appears the conclusion of the fantasy drama has left him in a very dark place.
Multiple sources tell Page Six the show's ending has "really hit him hard," and he is seeking treatment at a luxury Connecticut retreat.
Reports suggest he checked in weeks before the finale on May 19, and has been undergoing counselling, meditation sessions and behavioural therapy to combat stress.
"He realised this is it - this is the end; it was something they had all worked so hard on for so many years. He had a moment of, what next?" the source adds. "He's in the clinic predominantly for stress and exhaustion... His wife Rose (Leslie) is being extremely supportive. Everyone close to him really wanted him to get some rest. Right now, he just needs peace and quiet."
A statement from Harington's publicist to WENN reads, "Kit has decided to utilize this break in his schedule as an opportunity to spend some time at a wellness retreat to work on some personal issues."
The British actor recently told U.S. late-night TV host Jimmy Fallon he had struggled with the final scenes of the show, explaining, "I was very shocked and surprised at certain events... and then I blubbed my eyes out. I cried."
Kit was spotted at a Madison, Connecticut bookstore the weekend the final "Game of Thrones" episode aired. He told staff he was on "holiday" in the area, according to local reports.
He told Esquire in April he had a "full-on breakdown" after filming his final scenes for the drama.
"(On) my final day of shooting, I felt fine... then I went to do my last shots and started hyperventilating a bit...," he recalled. "Then they called 'wrap' and I just f**king broke down. It was this onslaught of relief and grief about not being able to do this again."