If you have a false impression of a person's character because you've jedi mindtricked yourself into not thinking the worst of people, you might end up trusting an untrustworthy person.
If you are in a toxic work environment, and you convince yourself it's not so bad, you might end up staying in a situation that is actively harming you.
We are speaking in the abstract and I can't comment on anyone else's experience. But I personally find toxic positivity and the endless drive to be more productive much more dangerous than being too negative.