I'm not sure the scientists have quite the right grasp of the situation. They seem to think that pessimism skews the choices. That is, they see it as a distortion, a wrong choice. So they're probably imagining that if they could somehow alter the choice to it's pre-pessimism state, it would work out just as well. That's not necessarily the case. There are two subtler factors in play here: energy and enjoyment. The study employed two elements, a negative stimulus and a positive reward. It's accurate to say that the responses changed, but only accurate to say "skewed" if the negative stimulus had the same level of annoyance and tolerance, and the positive reward had the same level of enjoyment, as the pre-pessimism state. And that's not what happens with depression and anxiety, which the study is trying to observe indirectly through this analogy. Both of those conditions tend to lower people's energy; they have fewer spoons to spend on enduring unpleasant things. And both conditions also tend to lower people's enjoyment of positive things. That is, if they made the same choices they used to, they would experience a constant barrage of miserable stimulation they're not equipped to resist, thus running down their health even more. Conversely, experiences that used to be pleasant now deliver much less enjoyment. The cost is higher but the payoff is lower. That makes it not a good gamble anymore. If the point of going to a party, which requires putting on party clothes, going out, spending money on gas or a bus, maybe walking through the rain, etc. -- all of which can be unpleasant -- is to enjoy yourself, and when you get there, little or no actual fun is had, then the effort was a waste. Sensible people learn not to do that again, at least not until the circumstances change to make it a better deal. This also assumes they have a spoon to spend on thinking through the analysis at all. Often, no they don't, so they do what avoids spending energy they don't have: by saying no.
So if you're dealing with depression, anxiety, or other challenges then the risk-benefit analysis is more important than to someone with tons of emotional energy to spare. It's the spoon theory all over again, just for mind instead of body. You have to think about what the risks and benefits are, then test your theory. If you're not getting anything out of an activity, drop it, no matter how much other people whine. They're not dealing with your brain. If you find that you hate going to parties, but once you're at a party you have fun, then you have a different challenge -- getting past the part of your brain that doesn't want to do the going part. It's just more work to get at the fun part. And you have to keep looking at the results over time, because they can change. Which activities or choices work better?
It's not just people with mental issues who face this challenge. It's anyone for whom socializing is extra risky or tiresome for any other reason. Say, fat people, who run the risk of having total strangers harass them every time they put on clothes, leave the house, or eat food. Or queer people or transfolk, who daily run the risk of getting beaten to death for existing. Black lives don't matter to white cops either. How much do you really want to go to that party? Is it worth the risk, to get the payoff?
The question came up in college, because female-bodied people were warned not to do things that had a high risk of rape. I couldn't imagine why anyone would risk going to a frat party. But then, I don't enjoy parties. Other people considered it worth the risk. They couldn't understand why I'd risk walking to a library alone. Well, it's pretty simple; you get between me and my books, I shred you. Different risk-benefit analyses, because each of us had not only different needs and skills, but different levels of reward at the end of a choice. I could've gone to the party, they could've gone to the library, but neither of us would've gotten the reward that the other person did from that activity. It's not there for everyone. Only the location is. And that's not exactly obvious to everyone.
It's straightforward to study the fact of a choice. It's a yes-no question in that study. But the meaning of the choice -- the subjective accuracy of whether it was better one at that moment -- isn't so simple to measure. That way lies giving people very rigid, very bad advice.