Complacency is a dangerous satisfaction with how things are, combined with a lack of awareness that problems might be developing. When someone becomes complacent, they stop paying attention, stop trying as hard, or stop preparing for challenges because they assume everything will keep going fine.

A soccer team that's winning easily might become complacent and stop playing their best, giving the other team a chance to catch up. A student who aced the first few tests might become complacent and stop studying, then struggle when the material gets harder. A ship's crew that becomes complacent about safety checks might miss a small problem before it becomes a serious one.

Complacency isn't really about being pleased. It's about being too comfortable, so comfortable that you forget to stay alert. A complacent runner might assume they'll win without training hard. A complacent business might ignore new competitors until it's too late.

Complacency sneaks up on people precisely because things are going well. Success can make you complacent if you forget that success usually requires continued effort and attention. The opposite of complacency isn't worry or anxiety, but staying engaged, alert, and ready to adapt when circumstances change.