Consider the frailty of our species.
We are bags of water, easily punctured. Dropped from any height over 20 feet we splat. Creatures too small to be seen can kill us. Our nervous system has a poor signal-to-noise ratio. We will perceive things that are not there. We will believe without any good reason to do so. We are driven by our emotions; reason is merely the servant to assist in obtaining our desires. We must be lucky, in the extreme.
We are the heirs of a long line of lucky beings. Our greatest mistake will, I believe, turn out to be thinking we have it made.