IPA: /kəmˈpleɪsəns/
KK: /kəmˈpleɪsəns/
A feeling of satisfaction with oneself or one's achievements, often leading to a lack of awareness of potential dangers or deficiencies.
His complacence about the project made him overlook important details that needed attention.
Complacence is formed from "com-" (meaning together) and "placere" (meaning to please). The word describes a state of being pleased with oneself or one's situation, often to the point of being unaware of potential dangers or deficiencies.
Think of being 'together' ('com-') with a sense of 'pleasure' ('placere') — that's why complacence means being pleased with oneself.