S6E07 Explained – update #1 (Patreon)

In the books, Jaime has complicated feelings about the Siege of Riverrun. One issue is that, in Storm, when Catelyn frees Jaime from captivity, she makes him swear that he will "never again take up arms against Stark nor Tully". And Jaime thinks on this when he's at the Siege:

"If he could end this siege without bloodshed, then it could not be said that he had taken up arms against House Tully"

"If the Blackfish would not listen, he would have no choice but to break the vow he’d made to Catelyn Stark"

This impacts the way Jaime sees himself and his personal honor:

"He would need to storm the castle. Well, what’s one more broken vow to the Kingslayer? Just more shit in the bucket"

Another complication is that, as a youth, Jaime idolised the Blackfish:

"at that age, no girl interested Jaime half so much as Hoster’s famous brother, who had won renown fighting the Ninepenny Kings upon the Stepstones … pressing Brynden Tully for tales of Maelys the Monstrous and the Ebon Prince"

So Jaime is now forced into conflict against a hero he once looked up to, and against a family he swore not to attack. On top of that, he's still reeling from the death of his father Tywin, his fallout with Tyrion, and his deteriorating relationship with Cersei (in the books). So during the Siege, Jaime is dealing with a heap of conflicting feelings – "the human heart in conflict with itself", indeed.