To act in a way that causes one's own failure or problems, often due to self-sabotage.

अपने काम में खुद को बाधा डालना

English Usage: He could have won the race, but he was being his own worst enemy by doubting himself.

Hindi Usage: वह दौड़ जीत सकता था, लेकिन आत्म-विरोधी होकर उसने खुद पर शक किया।