Correctly assessing the risk doesn't mean "I don't do anything that has an unlikely possibility of a horrible outcome", it can mean "I decide that I'm OK with that possibility and do it anyway, because I think the benefits outweigh the possible drawbacks". If you then do get unlucky and catch a nasty disease, that should not change your post-recovery decisions about going on holiday a second time: your risk/reward tradeoff should still be "I'm OK with the possibility of a bad outcome".

Re "It is a human nature to overreact (post-factum) to an unlikely event" -- yes, absolutely agreed. This is what I mean by saying that humans as a species are terrible at assessing low-probability risks. That most people change their view just means that most people both underestimate the likelihood of low probability events that haven't happened to anybody they know, and overestimate the likelihood of low probability events that have happened to somebody they know.

Agreed on both the definition of the optimal assessment and on the fact that the humans are bad at it. I actually think this (humans being bad at it) is good for the civilization as it helps people try things they would be too scared to do if they properly assessed all the potential outcomes with their probabilities.