perseverance
堅忍不抜の精神で困難を乗り越えた。
He overcame difficulties with unyielding perseverance.
堅忍の末にようやく目標を達成できた。
After much perseverance, the goal was finally achieved.
堅忍を旨として日々の鍛錬に励んでいる。
He devotes himself to daily training with perseverance as his motto.