(Hopefully you don't mind an example from someone else; I seem to do similar, but can't speak for the original poster :))

As a random recent example, the probability that anything goes wrong with my equipment while SCUBA diving is fairly low to begin with, since I get the gear from a trusted source and know they do good maintenance on it. Even if something goes wrong, I know techniques for handling everything but a catastrophic failure by myself. Even if my gear fails catastrophically, I still have a buddy, who I know personally has been trained to handle that situation. Even if the gear both of us has fails catastrophically, or my buddy panics, or isn't nearby, there are emergency techniques that risk injury but will avoid death.

I actually used similar logic to get myself to learn in the first place - "right now, this seems dangerous, because I do not know how likely the risks are, nor how to mitigate them, nor how to handle emergencies. Between taking classes and doing some research, I can alleviate both of those. The cost of these actions is acceptable even if I decide part-way through that this is too risky for me. Therefore, I will go ahead, sign up for a class, and make a serious commitment to drop the class if I ever feel that SCUBA diving, or the way the class is being taught, places me at serious risk."