it makes sense why the body builds tolerance to psilocybin so rapidly and half life is quite long (at least a month or two) for evolutionary purposes. which to me is interesting because it shows that we've evolved to build tolerance against it but THC takes far longer and in very high doses to build tolerance.
all in all, I've read accounts of people seeing positive changes with microdosing but for my case, while I did not take heroic doses (McKenna's 5 grams), I took at best 2 to 3 grams. In higher doses I had a transcendental experience....
while nobody has died from taking psilocybin outright, there had been reported incidents where it had impact on somebody prone to schizophrenia and psychosis. However its extremely rare. This is why I suggest to people to have a sitter and be at a ground level.
It's not an issue for the millions of people that take it but if you've never even smoked marijuana before and this is your first try, please get a sitter.