A feeling of satisfaction with yourself or things as they are, especially when you're not aware of problems or dangers.
From Latin 'complacentia' (satisfaction, pleasure), from 'complacere' (to please greatly). The meaning shifted from general satisfaction to the modern sense of dangerous self-satisfaction.
Complacency is why people often fail after early success—your brain literally stops searching for problems once it feels pleased, which is why every successful company warns its employees against it.
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