It's also horrible advice on many levels. It leads people to internalize everything: everything is their fault, for "feeling this way about it" to "not fixing it" when in fact you can't do anything about it and it is literally outside your control.

There's a famous (oooold) study in German sociology, the unemployed of Marienthal. A factory closed, the town died, people got all laid off. Nothing they did caused this, it was in a downturn and it just hit that town. The workers in that factory supported each other and all knew this wasn't their fault. They lost a lot of income, yes, but they didn't blame themselves and didn't fall into a black pit because of that. It was, for them, from their POV, unfair, but they weren't consumed by self-doubt because they framed it this way: unfair, not my fault.

The managers, on the other hand, with their social circle outside of the city, were excluded from their circles, gradually: they were in a culture in which the others did at least tacitly assume it was their fault, and the managers themselves also thought it was on them. That wasn't great for their future development. They did get consumed by self-doubt.

Sure, "life isn't fair or unfair, it just is", but from the position of people, it sure looks fair or unfair to them, and both of these takes are real. You can find people who thought all was fair in the example, and people that didn't, and it really is beside the point to argue over who's right. The point is that there are external influences that people can't control, no matter the moral assessment of those.

But psychology can't stand that. This is a larger problem of current psychology: it internalizes everything into behavior and body functions, learned practices and chemistry, and forgets there is a world out there outside the person (a common ailment of contemporary society). It does so for purely pragmatic reasons: the individual is something the profession of psychology can work on (and bill them for). it can't change the economic situation in a town, power dynamics at work, structural changes in an industry, technological developments, etc.

Another rule of organizational sociology: Organizations see the world through the lens of their practices. They order the world in categories they can be "responsible for" and work on, as that means they get to offer services and increase their prestige. They are allergic to any view of the world that takes away responsibility (and ability to do something) from them. This is what "causes" this bad, terrible, horrible advice.

snowflake psychology.

Life isn't fair. The fact that we exist is incredibly lucky and that's not fair. The fact that we're having this conversation on a computer while so much injustice rains in the world. That's not fair. Our existence is an incredibly lucky, miraculous circumstance and we didn't deserve it, but we better enjoy it!