愚行

1. Origins, structure, and basic meaning

• Structure: 愚行(ぐこう) denotes an act judged to be foolish.
• Basic usage: It describes regretting one's foolish act of tearing up a letter in anger.
  • 怒りに任せて手紙を破った自分の愚行を悔やんだ。

2. Common pitfalls and similar expressions

• An unsuccessful result and a judgment of conduct
  • 失敗(しっぱい) can describe an unsuccessful outcome. 愚行 criticizes the act itself as foolish, making its evaluative tone more direct.