Aware people never stop looking for it.
"It", in this instance, is a black swan, AKA "an unpredictable or unforeseen event, typically one with extreme consequences".
Of course the extreme consequence could be a good thing . . . like winning a $multi-million lottery. No ticket purchaser actually expects to win the big prize so it can legitimately be referred to as unforeseen . . . definitely an outlier. But the color black (properly an absence of color) is commonly associated with something sinister, and like that horrid creature lurking under a child's bed or in the darkened closet a black swan is legitimately something to be feared.