4 ideas
On his last Gateway mission, Robinette Broadhead's two-ship expedition is caught near a black hole. Only one craft can escape, and in the scramble Robin ends up in the ship that breaks free while his lover Klara and the others stay trapped at the edge of the event horizon. He returns rich from the scientific bonus and spends years unable to decide whether he saved himself on purpose or by accident.
Gateway prospectors board alien Heechee ships whose destinations are fixed in controls no human can read, so every launch is a lottery. Some ships return with a find, some return empty, and some return with the crew dead or never return at all. The system runs on poor people from places like the Wyoming food mines, who accept high odds of death because a large bonus is their only way out of a life with no other exit.
Near a black hole, time runs slower for someone deep in the gravity well than for a distant observer. From outside, a person falling toward the horizon appears to slow almost to a stop and is never seen to finish falling. So for Robin, decades pass while only seconds pass for Klara, and the moment he left her never becomes past for her. The novel uses this correct physics to make his guilt concrete: it cannot fade because the event it concerns is, in her frame, still underway.
Robin's sessions with the robot therapist Sigfrid von Shrink proceed by avoidance: he jokes, spars and changes the subject, and each detour moves him closer to the black-hole memory he is repressing. The resolution is not being cleared of blame. It is being able to feel the full guilt and keep living, which shifts the goal of therapy from getting rid of the pain to carrying it.