YOU SAID:

the only opinion about yourself that matters is your own

INTO JAPANESE

自分自身について唯一重要な意見は自分自身の意見である

BACK INTO ENGLISH

The only opinion that matters about yourself is your own opinion.

INTO JAPANESE

あなた自身について重要な唯一の意見は、あなた自身の意見です。

BACK INTO ENGLISH

The only opinion you have of yourself that matters is your own opinion of yourself.

INTO JAPANESE

自分自身についてあなたが持つ唯一の重要な意見は、あなた自身の自分自身の意見です。

BACK INTO ENGLISH

The only opinion you have of yourself that matters is your own opinion of yourself.