Jaime Lannister, on the other hand (it's a joke!), might slowly come to the realization that his sister is mad… just not this week. Euron's continued cockiness is irking Jaime, even when his sister-lover seems immune to the charms of Emo Rock Iron Born. Plus, Olenna Tyrell's final, forecasting confessions -- that Cersei will lead to Jaime's end -- do look like they weigh on him. As a girl Cersei was told a prophecy that she would die at the hands of her valonqar, the High Valyrian word for "little brother." Book readers suspect the reverse might be true.
Part of the episode description for this week said "Jaime learns from his mistakes," and the reference to the Battle of the Whispering Wood is a reference to how Jaime got himself captured in Season 1. Jaime was heading the Lannister forces laying siege to Riverrun while his father Tywin was trying to hold off Robb Stark's army from reinforcing the Tullys, when a scout reported 20,000 Stark men marching towards Tywin's forces. Thinking that was the bulk of the Stark army, Jaime was lured into the woods outside of Riverrun attacking what he thought to be a Stark scouting party, but which ended up being Robb's army. Robb sacrificed 2,000 men to Tywin's forces while he took Jaime prisoner and ended the Lannister siege of Riverrun. Jaime learns from his mistake by pulling this same trick on Tyrion this episode, leaving a small force at Casterly Rock while taking the Lannister and Tully army to Highgarden instead. So he's not completely off his game.