过犹不及 guòyóubùjí
(1) [going too far is as bad as not going far enough] 做事做过了头,就如同做的不够一样。指做事以适当为贵
子贡问:“ 师与 商也孰贤?”子曰:“师也过,商也不及。”曰:“然则 师愈与?”曰:“过犹不及。”——《论语·先进》
(2) (师,指子张;商,指子夏;愈:较好)