A single bad event outweighs several good ones of equal size
A sweeping 2001 review of research across memory, relationships, feedback and decision-making concluded that bad events and emotions consistently affect people more strongly than equally sized good ones, and get processed more thoroughly by the brain. It takes roughly five positive interactions to offset one negative one in a relationship. The authors argued this asymmetry is an evolved feature: reacting strongly to threats mattered more for survival than reacting to small gains.