Now I'm wondering if the part about "enjoyment" wasn't mere psychoanalysis but something I either unusually lack, or which is unusually obscured from my sight.

Enjoyment isn't the right word, I don't think. My wife and I both described the "Bruce effect" sensation as being more like a sense of recognition or rightness -- like confirmation of something that you expected, something that's just the way the world works. That, upon successfully losing, it's like, "yep, this is where I'm supposed to be". Not enjoyment... more like satisfaction... though that's still too strong. Closure, maybe? Relief? It's a brief and subtle reward, not a conscious pleasure.

It was just a loser side with bad habits, probably formed mostly by hyperbolic discounting or poor impulse control.

Anosognosia. Don't speculate, investigate -- observe the automatic thoughts in action, rather than adding voluntary thoughts on top of them.

And it occurred to me that I should give this side a name and separate it out from my real me.

Be careful of how you do that... dispassionate separation is okay, rejection is not. When people actively reject parts of themselves ("that's not me; I would never do that"), they make it more difficult to observe or change the actual motivation involved. ("After all, I would never do that... therefore it's irrational/bad/whatever.")

The way to remove something like this is to imagine what it's like when that part of you gets its wish, so you can get a glimpse of what the reward is. Then you imagine having that reward, and find out what, if any, reward is behind that... and so on, all the way to the root reward emotion, fully experienced in your body, and chain backwards through the same path by which you came, re-experiencing as though you already have the root reward... noticing the difference in available choices, i.e., "If I already have this feeling, do I really need to do X? Is it easier to get X?"

Once you've fully worked back to the starting point, you'll have changed the response options for the original behavior context -- i.e., the original response will no longer be compulsive.

This is a very short sketch of the technique; my shortest training on it takes over an hour and assumes at least a little prior mindhacking experience. (The technique itself can be applied in about 10-20 minutes after some practice, or with the assistance of an instructor/guide.)

There are a few subtleties, not the least of which is that you need to be able to actually pay attention to your autonomous responses without injecting conscious interpretation, speculation, or critique (e.g., "that's stupid, why would I want that?" etc.).

I don't think the "reward feeling" for losing at a video game is the same thing as what our "Inner Bruce" goes after. They may be related, I don't know. But losing as a video game can be fun, more than losing in real life. Fun in the same way the rest of the game is fun, it's not a special kind of fun.

I get that a lot in Spelunky, where you often make a small mistake and splat blood flies and you have to start over again. but it can be fun.

That's an important distinction between hardcore and casual games. Some players don't mind getting killed horribly and having to start over again - it's what they expect. But other players will be discouraged and feel bad if the game tells them that they suck. That's why most casual games are very nice to the player, and often you just can't lose at all. A decade or two ago, the game industry was mostly focused on hardcore players; recently they have found out you can make a lot of money with casual games (targetting "middle aged women"), but you have to make the games differently.

Maybe it's because hardcore players expect to die over and over in video games, and they know viscerally that it doesn't matter at all, so when they lose, they don't have any negative associations. On the other hand, new players haven't made that dissociation, and feel bad about losing.

I never thought much about the relationship between "self-sabotaging to lose in real life" and "enjoying losing in video games", it's interesting ...

Personally, I've only really noticed this reaction in myself in an academic setting with moving goalposts. If I'm putting effort into something I find at least mildly stressful, and success is "rewarded" with heightened expectations and further obligations, I develop a desire to prove that I'm capable of melting down and failing. The hypothetical satisfaction derives more from the thought of specific individuals observing my failure than from the failure itself.

Perhaps you've haven't optimized much against pathological incentives?

Most poker players, even the losing ones, don't like losing, but I think it is sometimes a driver for losing players continuing to play. Sometimes it is self-hatred (vindicating the feeling that you don't deserve to win). Sometimes it is the desire to whine - to have something bad happen to you that can plausibly be blamed on someone else.

Actually, from what I have read, feeling like one doesn't deserve to succeed, and self-sabotaging, and feeling some kind of sick satisfaction when one fails, is pretty common.

I propose a good word to use instead of enjoyment would be "drama" or "intensity". If losing has become a personal narrative, an instance of losing feels like a turning-point in the plot.

Interestingly I have the opposite response. I genuinely don't understand how some people get so much pleasure from the act of winning, to the extent they will cheat or subvert the game (or in the longer term memorise moves by rote). Generally I enjoy the process of playing the game and will be annoyed at myself if I make particular mistakes that cause me to lose, but if I play to the best of my ability, enjoy it and my opponent simply plays better I wouldn't be upset.

[Standard disclaimer about difficulty of self reporting internal states and the possibility of rationalisation applies, its possible I have a strong self image as someone uninterested in winning.]

Kill me more, please! ;)

Have you ascended in Nethack?