Not one of your pertinent ancestors was squashed, devoured, drowned, starved, stranded, stuck fast, untimely wounded, or otherwise deflected from its… - Bill Bryson

Consider the fact that for 3.8 billion years, a period of time older than the Earth's mountains and rivers and oceans, every one of your forebears on both sides has been attractive enough to find a mate, healthy enough to reproduce, and sufficiently blessed by fate and circumstances to live long enough to do so. Not one of your pertinent ancestors was squashed, devoured, drowned, starved, stranded, stuck fast, untimely wounded, or otherwise deflected from its life's quest of delivering a tiny charge of genetic material to the right partner at the right moment in order to perpetuate the only possible sequence of hereditary combinations that could result — eventually, astoundingly, and all too briefly — in you.

So I decided to do it [hike the Appalachian Trail]. More rashly, I announced my intention - told friends and neighbors, confidently informed my publisher, made it common knowledge among those who knew me. Then I bought some books... It required only a little light reading in adventure books and almost no imagination to envision circumstances in which I would find myself caught in a tightening circle of hunger-emboldened wolves, staggering and shredding clothes under an onslaught of pincered fire ants, or dumbly transfixed by the sight of enlivened undergrowth advancing towards me, like a torpedo through water, before being bowled backwards by a sofa-sized boar with cold beady eyes, a piercing squeal, and slaverous, chopping appetite for pink, plump, city-softened flesh.

You can get some sense of the immaterial quality of clouds by strolling through fog — which is, after all, nothing more than a cloud that lacks the will to fly.