I was talking with my dad recently & we got on the topic of People Thinking They Can't Do Things, and like, he is at his core a well-intentioned person who genuinely wants the best for others, but he has definitely internalized some harmful ideas a la "anyone can do anything, the only thing stopping them is their own attitude". so I was like. I see where you're coming from, but let me tell you a story.
last year, I worked with 10 year olds- many of whom had never really spent time outdoors- in an outdoor education program where they came to spend a whole week doing shit outside in nature. the top two scariest experiences for these kids were 1) very tall metal tower, and 2) walking outside at night in the dark with no flashlights.
I tried a lot of different things to persuade them all to join me for each experience: I presented it with enthusiasm and passion, I did physical demonstrations and scientific explanations to help them understands how safe it was, I voiced my absolute commitment to their safety, I invited them to brainstorm ways to help each other and themselves feel safe, etc.
generally I always had at least 2-3 kids out of about 10 who opted out, or if they did join me, would spend the entire experience crying and freaking out. when it was over, they would conclude that even though they did not die- or even get hurt- it was so scary that it wasn't worth it and they never wanted to do it again.
then I changed the question I asked. instead of asking them to tell me whether they could do it or couldn't do it, I asked them to raise their hand for one of three options:
You can definitely do this.
It will be hard or scary or uncomfortable, but you can try to do this.
It will definitely be too hard, scary, or uncomfortable, and you cannot or should not try to do this.
suddenly, almost nobody was opting out of these experiences.
they would try, even if they were scared, because they know that being scared didn't necessarily mean that they couldn't do it at all. and more importantly, they knew that if they needed to stop, that was an option; they weren't trapped in their decision to try.
and the real takeaway here, for me, is in the nuance: people need to be able to challenge themselves and to be uncomfortable in order to grow, and people need to be able to opt out in order for opting in to be a safe option.