It actually works for some, but not for the reasons people think it does… If there is going to be a promotion, happy, or at least happy looking people are far most likely to get it, so they can motivate others. In most cases, this selection is based on internal biases rather than explicit requirements, but there are many people in power who actually consider it as a factor.

Another one is the impostor syndrome, those techniques make you believe you deserve anything good coming your way, and think yourself responsible for anything positive that happens in your life, so just like religion, if you got it it is thanks to you for believing in that higher power, and if you didn’t, it is beecause it wasn’t the time, your deity of choice has something better waiting for you, because ultimately it wasn’t going to be good for you, or because you didn’t pray/believe/manifest it good enough.

They try to cover self doubt with a bandaid and confirmation bias, which can work, and make the people who follow those tenants more secure, more willing to take risks, and more easygoing, but also makes them far more prone to mistakes and being too stubborn.

For the most part, keeping a happy face works just the same, and people who believe this things are so delusional, multiple people at work told me it was because of my change in attitude that I won a raffle, when that change in attitude was not because of that bullshit, but because I had given up and was already looking for a new job, and completely stopped doing work stuff on my free time just to keep up.