I don't think many players truly understand how brutal and sustained downswings can be. Fewer still are able to continue to make good decisions and be confident in doing so when they are losing 2-3BI pretty much every session for 5-15 sessions (I know I can't and regularly accentuate downswings). The build up of pressure can become huge over these times in particular and it's natural to not want to relive those emotions, but having that resilience to get back in the saddle sorts out the wheat from the chaff in any walk of life. I'd go as far as to say that if you can use poker to develop your resilience, you're going to see huge benefits to the rest of your life too.

The most relevant thing to me that I've read with the mental game is that the build up of pressure can be dramatically heightened by not having a strong technical approach. For instance, getting majorly tilted by the constant pre-flop 3betting is only because you don't have a strong and well-reasoned technical approach for dealing with it yet. If you don't have that reasoned approached, you'll only end up releasing that pressure by doing something stupid like jamming ATC in a bad spot. Likewise, if you don't truly understand variance through experience, you're not going to handle that pressure well either. That said, I think working on other aspects of the mental game is more important than the technical side if you're smart enough to grasp the technical aspects pretty easily.