Not long ago, while I was working on a game engine, I couldn't have imagined joining one of the most renowned software companies, while working with a completely different tech-stack. I was so specialized that I could see through the compiler and the processor, but I wasn't able to create the simplest mobile app, or deal with the most basic database.
My world was small. Scalability was a non-existent issue. A running program is just a process where functions call each other! Yes, I do know that servers and databases exist (You've all played MMORPG, right?), but had you asked the then-me how to design a view counter, I would tell you that it's just a variable backed by a SQL database!
I knew the fresh start was going to be difficult, but I didn't know it would be this brutal. All the shiny buzzwords, the numbers in the dashboards, the endless stream of work posts, the products backed by thousands(!) of engineers, oh my! How could one ever work if one must keep these constantly in one's mind?
I had a flashback to when I transitioned from an eSports gamer to game developer, some 10 years ago while I landed my first job. I was barely able to program in scripting languages, let alone these fancy graphics pipelines. My APM (Actions per minute) was still higher than lines of code I could write on a good day. It wasn't like turning an F1 driver into a coach, but more a driver to automobile engineer.
It was a complete reconstruction of my cognition (= how things work), and my understanding of actions (= what I can do) in the environment. It was a strange feeling: Important things no longer mattered, old guidelines failed to apply, and the previous way of describing the world fell apart. Afterall, my perception of the world is my distorted illusion, and existing notions can be neither the whole picture nor entirely accurate, but merely good enough for me to survive. It was these baby steps of relearning how to talk, how to 'walk' (as in, navigating through people and matters in the new organization), and even how to think, that made me who I am now.
Painful, tired, constantly feeling not myself, I survived. It was worth it. I could have been more successful in the old place, but I followed my* heart. Getting out of the comfort zone was not only difficult because of the level of determination it required. From what I can tell, it is equally challenging for some of the most competent and ambitious people. They consider it unimaginable, not because they can't acquire new skills, but because they couldn't let go of the old experience built on years of hard work.

There is a metaphor I enjoy, that pursuing endeavors is like hiking in a tall mountain. It may be tempting to reach the peak, but the closer it is to the top, the more challenging it will be to rise further. Many of us end up being stuck halfway up and come to realize that the peak isn't the most rewarding accomplishment, nor is it even the aspect about the hike which we enjoy the most.
Yet, we hesitate to change our goal because it seems impossible to get there! Indeed, there is no shortcut to get from one mountain to another, and initially every direction seems downwards. I think the one trick that really enables one to flee from this local maximum is stop planning greedily. The future is unpredictable, and there is never a highway from one success to the next.
I am so glad that I am still hanging in there - after having written more than 300 pages of tech notes and countless meeting memos. Things all start to make sense again!
Along the way I was asked by the others, "but we are X. How could you, and why would you become a Y?" There is no simple answer. The way I see it? I am not just the past me, the present me, but also the future me which I choose to become - if we ignore views such as no continuum in identity or no free will.
I choose to become the future me. How about you?
* That of ego, not id, but don't ask me why at the time I believed in Freud who is now considered pseudoscience
** The Climb, one of the first VR game on Oculus Rift, by Crytek where I worked in my previous job.