YOU SAID:

I can't describe how sad seeing you in that clown costume makes me

INTO JAPANESE

私はそのピエロの衣装であなたを見ることがどれほど悲しいかを説明することができない

BACK INTO ENGLISH

I can not explain how sad it is to see you in that clown costume

INTO JAPANESE

私はそれがそのピエロの衣装であなたに会うことがどれほど悲しいか説明することができません

BACK INTO ENGLISH

I can not explain how sad it is to see you in that clown costume