What is the negativity bias?

Negative events, emotions and information affect us more strongly and stick with us longer than positive ones of equal size.

The mechanism is evolutionary: an ancestor who ignored a good berry lost a snack, but one who ignored a predator lost everything — so brains that weighted threats heavily survived. Bad therefore "outweighs" good in attention, memory and emotional impact, even when they're objectively balanced.

Example: A performer who gets ninety-nine glowing reviews and one cruel one lies awake replaying the single cruel one. A single insult can outweigh a string of compliments.

Tip: When one bad thing is dominating your whole picture, consciously count the positives it's drowning out — they were probably the larger pile.