“to think of the possibility of danger in a safe condition; to be prepared (to handle accidents)”
虽然处在平安的环境里，也想到有出现危险的可能。指随时有应付意外事件的思想准备。
Origin 《左传·襄公十一年》：“居安思危，思则有备，有备无患。”
Example 得宠思辱，～（清·钱彩《说岳全传》第六十回）
Press ? anytime.