WARNING: Spoilers for Game of Thrones season 8, episode 4.
Jaime Lannister made his choice in Game of Thrones - and it was sister Cersei rather than the much more likable Brienne of Tarth. Jaime's romantic life has always been at the core of the HBO fantasy series - his incestuous affair with twin sister Cersei created two illegitimate Kings, led to him pushing Bran out of the window, and has been the motivator for multiple popular fan theories.
But for many, Cersei was never his true love. That was Brienne of Tarth, sword to Catelyn Stark who transported a captured Jaime south after he was captured in the Battle of the Five Kings. He bared his soul to her, revealing the truth of his oath-breaking Kingslaying and forming a strong bond. They've been distanced for much of the show since season 4, but properly reunited in Game of Thrones season 8, episode 2 where Jaime Knighted Brienne, and in episode 4, they finally made their feelings physical.
However, this is Game of Thrones, and nothing is happy forever. Later on in the episode, titled "The Last of the Starks", Jaime decided to leave Winterfell - where he'd initially planned to stay with his new lover - to return to King's Landing to be with Cersei (who was busy this episode killing dragons). Why did he choose the murderous Queen over the loyal Knight?
The simple answer is rather tragic. Jaime is one of Game of Thrones most rehabilitated characters, even cleared of what he did to Bran by the Three-Eyed Raven himself, yet when faced with a crossbow-wielding Bronn and anti-Lannister sentiment, he realizes who he really is (or, at least, who thinks he is). For all the good he's done and all the positivity he's received from the likes of Bran, Tyrion and Brienne, he still feels a bad person - and the powering reason for that is his love for Cersei. He leaves to be with the person who reflects that side of him; the person who, to Jaime, he deserves.
This is surely not going to be where Jaime's arc ends, however. As early as Game of Thrones season 2 it was clear the Golden Lion wasn't at heart the monster audiences first suspected, and it would be a betrayal of almost a decade's worth of TV for him to just revert. Instead, this is likely Jaime's final test, with his eternal love for Cersei set to be challenged as the last war begins (something Missandei's death ensures has begun).
It may be that, far from going to be with the woman he loves, Jaime will end up killing his sister. Queen Cersei's death has been teased in various forms across the series, including season 8, and one major book fan theory has Jaime turning Queenslayer. If the expectation that King's Landing will be destroyed or threatened comes to pass and it's Cersei lighting the fuse, there would be a tragic circle to Jaime's story that still sees him redeemed. The question is whether he'll survive to return to Brienne.
Game of Thrones continues Sundays at 9pm on HBO.