But how often does the lesson actually “take”?
Literally: pain – determine – think – pain
Alternately: Remembering pain after one has recovered from it. By extension, looking back on something negative in the past (including e.g. one’s mistakes and failures) and taking it as a warning about what to do, or not do, in the future.
Notes: This is another gift from our friend, the Tang-era Chinese scholar Han Yu (韓愈, Japanese Kan Yu), and is a compound of compounds. While 痛定 is not used in contemporary Japanese, in Mr. Han’s usage it meant recovery from disease, and in the same way 思痛 meant remembering that disease.