Nobody knows everything.
No matter how much we learn, we're always operating with flawed models of the world.
But reality doesn't go easy on us.
Even the most understandable mistakes can be fatal. Lives can be torn apart (sometimes permanently) by good people with good intentions.
How to account for this?
By assuming the worst, and working toward the best.
Even if everything we do goes as painfully wrong as possible, it's still better than doing nothing.
Smart mistakes beat stupid mistakes, but some mistakes beat no mistakes.
As long as we get our thoughts in order.