the fish can tell whether the water is hot or cold; none but the wearer knows where the shoe pinches ❍ 况且“～”，用庸俗的话来说，就是“自家有病自家知”罢：……(鲁迅《故事新编·序言》2) Besides，“The fish can tell whether the water is hot or cold.”In vulgar parlance，“A man knows his own illness.”