So about surprises and playing against your best interests.
A while ago in our Blades game our characters were negotiating with an antagonist but not actively hostile powerful NPC and their gang. We needed to get certain information from this NPC. My character had as part of his backstory that his parents were killed in a fire. It was just distant background, and I had not been thinking about it in a while. But then in midst of this discussion, this NPC accidentally reveals that they were one who was responsible for that fire (they did not know how it related to my character.) And they were very callous about it. They had not had anything personal against my character's parents, they were just a sacrifice, some insignificant trash to the NPC. And at that moment I knew my character would try to kill that smug bastard there and then. My internal model of the character said that this is what they do, no question about it. It was not so much a choice than a revelation. So a fight ensued, I killed the SOB, my character got trauma, people got hurt, and we did not get the information we needed from the NPC. It was surprising, and it was not tactically smart. But it was very cool moment.
This is the sort of stuff I want to be happening.