Well obviously I presented this feeling as irrational, but if your are looking for an interpretation of our underlying instinct and a meaning behind us feeling threatened then I think I can come up with something.
I believe we worry that even if someone pursues something superficially matching your own goals they might miss the deeper meaning and goals behind your actions. Even if they are immitating you in some shallow way, they might still be "doing it wrong", and you are afraid that you aren't good enough to articulate a proper correction to their behavior.
There's also the idea that the only reason you chose your current hobby is because you believed you had something unique to contribute, and it might upset you that they apparently didn't realize what they were doing wasn't unique, didn't consider all of the other options available to them, or they didn't somehow give an indication that there was a prior interest in pursuing that exact thing you have focused on.
Anyway, I guess the point of my post isn't to say that feeling bad at "being replaced" is wrong, but rather that it's wrong to think you are the only one who can provide value to the world or generally achieve fulfilment in your specific way. Anyone can do what I do. They just often don't. And if they ever do, it will suck, objectively, but in order to live in the real world I just have to be prepared to do something else if that time ever comes.
Wow, I am not very concise lol!
