@remi 46yo here. I believe that by the time you get up there into your 40's you've had more than enough time to dig into a deep level of self-awareness. Whether that's (merely) time, or existentialism, mortality, or pattern-matching - you should know *yourself* well enough to recognize strengths, weaknesses, and how to effectively evolve.
@remi for me that was:
* starting a family (impetus to get incredibly serious about pretty much everything - life, health, etc)
* building a body of work where I could compare and contrast what worked well vs what didn't vs where I excelled and failed
* having worked at a significant amt of companies to pattern match who did a particular job well or not
All of that led to - "I'm a pretty good engineer. I'd be a better manager."
@remi The irony in my touting "self-awareness" is that the last statement above, "I am a good manager" -- I'm sure there are > 0 IC's who would call bullshit on it