noun, noun or participle which takes 'suru', intransitive verb
firm resolve; wholehearted determination
A yojijukugo meaning to make up one's mind and set out to accomplish something with strong, unwavering intention. Often used with する to describe the act of resolving to do something.
彼は一念発起して留学を決意した。
He resolved firmly and decided to study abroad.
一念発起して新しい事業を始めた。
With wholehearted determination, I started a new business.