[I mean the mental firmware to not get broken. When it is really broken, I feel often it might be hard to climb out without a dedicated help of a _psychiatrist_.]
The new things of 21th century might me discipline of dealing with unnatural abundance of pleasure/information/change/people, but simple countermeasures already pop into my head without too much thinking, like abstaining from read news or social media.
Or learning to ignore the cultural values spread by random people around. Homo sapiens are known for unconscious masochism by accepting harmful values and proudly battling them :-) I moved to Southern Europe, and I find it funny that people here are more joyful and content despite they earn less $$$ than citizens of depressed hardworking superpowers. Of course, they may have their own problems, but even on the subconscious level their facial expressions or postures perceived as noticeably relaxed.
Practicing/developing own philosophy, similar by the vibes to stoicism/buddhism, so I don't get broken enough to require a mechanic to fix me.
I find it very funny that nations who brag about having "science" and "technologies", proudly dismiss religion, but yet unable to come up with anything comparable to philosophical or religious systems, not talking about 100x improvements that terabytes of "scientific knowledge" bring.