I think one big issue is that people who are new to an exercise (or exercise at all) don't have a sense of scale, and don't realize quite how much progress they

I think one big issue is that people who are new to an exercise (or exercise at all) don't have a sense of scale, and don't realize quite how much progress they'll make early on. If you know some people can run marathons, it doesn't sound crazy to think "well, I ought to be able to run for 10 minutes without any problems", but there are a lot of people who would risk seriously injuring themselves with 10 minutes of quick-pace running. Not to the point of rhabdo, probably, but certainly not a healthy experience. It also doesn't sound crazy to think "Well, I'm in agony after two minutes, but there's no way that means I should stop. I'll never get anywhere with only two minutes of running!" But of course, 'beginner gains' are distinctive - someone who hasn't done cardio in years might be at two minutes today and six minutes next week. The only universal answer I know to solve this is to take your first few outings in a new thing lightly. Don't even set a training plan, just go out until you're a bit uncomfortable, then stop and see how you feel the next day.