Just out of curiosity, do you mean the person's self-confidence may dramatically improve with use? The only reason is because I had a recent co-worker who was laid off after taking psychedelics for a decent period of time. He effectively stopped contributing to the team and started making concerted efforts to get the CEO to establish a new, special position for him so that "real work" could get done and the "company would function 100x better."
Seeing the before and after was fairly dramatic. I tried to encourage them to stop using, but that "self-confidence" was so over the top that they ignored all of us and eventually lost their job.
I think GP was referring to the long-term mental resilience and mindset shifts that can be byproducts of trips, not the effects of being under the influence.
What you describe is a more manic "the world is centered on me" kind of egotistical confidence.
The one the OP describes is more of a "I survived everest so I can surmount this challenge" kind of confidence.
I'd argue the latter is more common in healthy use. The former arises from abuse. Either abuse of frequency, or not really taking care of yourself properly before/after a trip (like pulling an all-nighter or similar silliness). It sounds like your coworker was taking it with some regularity, potentially to perpetuate that sorta manic state.
My first experience was late 30s, I don’t know what it would have been like having that experience 17 or 18. I don’t know if I’d want my kids to have that experience at such a young age.
Psychedelics are profoundly strange. My before-the-experience expectations about what it would be like (having read an absolute shitload of literature and trip reports) and what it’s actually like were orthogonal.
A bad trip does equip you with a lot of confidence and resilience in yourself and your mental strength to almost get through anything. Once you’ve been through that (like seriously believing your reality is broken) a lot of other things in life seem easier.