"Fear of success" is a null concept; a name for a thing that doesn't exist in and of itself. The fact that the thing someone's afraid of is also labeled "success" (by the individual or others) doesn't make the fear special or different in any way. In essence, there's only fear of failure. It's just that sometimes one form of success leads to another form of failure. In other words, it's not "success" that people fear, just unpleasant futures.
Choking under pressure, meanwhile, is just a normal function of fear-induced shutdown, like a "deer in the headlights" freezing to avoid becoming prey. In humans, this response is counterproductive because human beings need to actively DO things (other than running away) to prevent problems. Animals don't need to go to work to make money so they won't go broke and starve a month later; they rely on positive drives for motivation.
Humans, however, freeze up when they get scared... even if it's fear of something that's going to happen later if they DON'T perform. This is a major design flaw, from an "idealized human" point of view, and in my work, most of what I teach people is about switching off this response or preventing it from arising in the first place, as it is (in my experiences with my clients, anyway) the #1 cause of chronic procrastination.
In other words, I doubt truels had any direct influence on "fear of success" and "choking under pressure"; they are far too easily explained as side-effects of the combination of existing mechanisms (fear of a predicted outcome, and fear-induced shutdowns) and the wider reach of those mechanisms due to our enhanced ability to predict the future.
That is, we more easily imagine bad futures in connection with our outcomes than other animals do, making us more susceptible to creating cached links between our plans... and our fears about the futures that might arise from them.
For example, not too long ago during a workshop, I helped a man debug a procrastination issue with his work, where simply looking at a Camtasia icon on his screen was enough to induce a state of panic.
As it turned out, he'd basically conditioned himself to respond that way by thinking about how he didn't really know enough to do the project he was responsible for -- creating a cached link between the visual stimulus and the emotions associated with his expected futures. (In other words, early on he got as far as starting the program and getting in over his head... then with practice he got better and better at panicking sooner!)
And we do this stuff all the time, mostly without even noticing it.
A "truel" is something like a duel, but among three gunmen. Martin Gardner popularized a puzzle based on this scenario, and there are many variants of the puzzle which mathematicians and game theorists have analyzed.
The optimal strategy varies with the details of the scenario, of course. One take-away from the analyses is that it is often disadvantageous to be very skillful. A very skillful gunman is a high-priority target.
The environment of evolutionary adaptedness undoubtedly contained multiplayer social games. If some of these games had a truel-like structure, they may have rewarded mediocrity. This might be an explanation of psychological phenomena like "fear of success" and "choking under pressure".
Robin Hanson has mentioned that there are costs to "truth-seeking". One of the example costs might be convincingly declaring "I believe in God" in order to be accepted into a religious community. I think truels are a game-theoretic structure that suggests that there are costs to (short-sighted) "winning", just as there are costs to "truth-seeking".
How can you identify truel-like situations? What should you (a rationalist) do if you might be in a truel-like situation?