I've been a software engineer for over 10 years I experience the IS all the time. I mean like on a weekly basis or something. I know it's kind of usual but I don't think that knowing that makes it easier. The fact that we all work in such a fast-paced industry kind of makes that more frequent, because we are faced with new challenges quite frequently: new jobs, new roles, new frameworks, new paradigms, etc. Everything is so new, you don't get to just use what you know very often, you just learn as you work. And here's the deal: it's not just learning that is hard, it's unlearning too.
I find that not being able to unlearn is often what causes me to experience IS: I either have some pre-made idea of how something should work, or how something was built and then I have trouble getting my head around that. Too often I find myself staring at some problem for minutes or sometimes hours trying to understand what's going on and this feeling starts growing inside "why is this so difficult?" or worse "why can't I get this right?" and it's really hard to avoid that, especially when you're working alone (in my case I work remotely, which makes things worse IMO). In my experience, it's also more frequent when you're starting a new job, because it's a time when you have to (un)learn a lot plus there's this pressure of showing what you're worth to a new team/manager /stakeholder.
What I try to do is to ask for help or just share my feelings with my wife. I know that our value as human beings is not defined in any way by our value as professionals (even though there's this social assumption that it is), but it feels better when someone else says that to you. So that's what I do.
I also think that IS gets worse with time for some people. In my case, I have never failed an exam or class, and the more professionally successful I become, the more pressure I feel to not fail and not disappoint the ones around me. So every problem I face kind of turns into this high school exam everyone is expecting me to ace, just like every other I have in the past, even though it's probably something small that would never get you fired.
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