Generally, if you want to go outside of your comfort zone, you might as well do something useful (either for yourself, or for others).
For example, if you try “rejection therapy” (approaching random people, getting rejected, and thus teaching your System 1 that being rejected doesn’t actually hurt you), you could approach people with something specific, like giving them fliers, or trying to sell something. You may make some money as a side effect, and in addition to expanding your comfort zone also get some potentially useful job experience. If you travel across difficult terrain, you could also transport some cargo and get paid for it. If you volunteer for an organization, you will get some advice and support (the goal is to do something unusual and uncomfortable, not to optimize for failure), and you will get interesting contacts (your LinkedIn profile will be like: “endorsed for skills: C++, object-oriented development, brain surgery, fire extinguishing, assassination, cooking for homeless”).
You could start by obtaining a list of non-governmental organizations in your neighborhood, calling them, and asking whether they need a temporary volunteer. (Depending on your current comfort zone, this first step may already be outside of it.)
What’s a good way to force oneself outside their comfort zone where most expectations and intuitions routinely fail?
This might become useful to build antifragility about expectation management.
Quick example—living without money in a foreign nation.
Is it possible to design a personal or group retreat for this?
What kills you doesn’t make you stronger. You want to get out of your comfort zone, not out of your survival zone.
Okay, natural catastrophes might not be a good example. (Edited)
Helping out with disaster/emergency relief efforts might get people out of their comfort zone.
Generally, if you want to go outside of your comfort zone, you might as well do something useful (either for yourself, or for others).
For example, if you try “rejection therapy” (approaching random people, getting rejected, and thus teaching your System 1 that being rejected doesn’t actually hurt you), you could approach people with something specific, like giving them fliers, or trying to sell something. You may make some money as a side effect, and in addition to expanding your comfort zone also get some potentially useful job experience. If you travel across difficult terrain, you could also transport some cargo and get paid for it. If you volunteer for an organization, you will get some advice and support (the goal is to do something unusual and uncomfortable, not to optimize for failure), and you will get interesting contacts (your LinkedIn profile will be like: “endorsed for skills: C++, object-oriented development, brain surgery, fire extinguishing, assassination, cooking for homeless”).
You could start by obtaining a list of non-governmental organizations in your neighborhood, calling them, and asking whether they need a temporary volunteer. (Depending on your current comfort zone, this first step may already be outside of it.)