self-conceit; pride
成功に慢心して努力を怠ってはならない。
One must not become complacent with success and neglect effort.
慢心が最大の敵だと師匠に教えられた。
My master taught me that conceit is the greatest enemy.
連勝が続いても慢心せず練習に励んだ。
Even with a winning streak, they practiced hard without becoming conceited.