YOU SAID:

I made a severe lapse in judgement

INTO JAPANESE

私は判断にひどい失墜をしました

BACK INTO ENGLISH

I made a bad mistake in my judgment

INTO JAPANESE

私は自分の判断で悪い間違いをしました

BACK INTO ENGLISH

I made a bad mistake at my own discretion

INTO JAPANESE

私は自分の判断で悪い間違いを犯しました

BACK INTO ENGLISH

I made a bad mistake at my own discretion