[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.