心こころに誓ちかう

expression, godan verb (-u)

vow to oneself; promise oneself; make a silent vow

Used when someone makes a firm internal resolution, often without speaking it aloud. Common in narrative and emotional contexts.

• 彼かれは二に度どと嘘うそをつかないと心こころに誓ちかった。

  He vowed to himself never to lie again.

• 私わたしは成せい功こうするまで諦あきらめないと心こころに誓ちかっている。

  I have promised myself not to give up until I succeed.