良薬は口に苦し (りょうやくはくちににがし): the most helpful advice may be difficult to listen to; good medicine tastes bitter
良薬は口に苦し
the most helpful advice may be difficult to listen to; good medicine tastes bitter
Good medicine is bitter in the mouth. Said before delivering criticism, or afterwards by the person who has decided to take it.
The same saying in Chinese: 良药苦口