得鱼忘筌（得魚忘筌）　

◎ 得鱼忘筌 déyú-wàngquán

[forget the means by which the end is attained;forget the trap as soon as the fish is caught] 筌是用来捕鱼的器具。得到了鱼,就忘掉筌。比喻达到目的以后就忘了赖以成功的东西

筌者所以在鱼,得鱼而忘筌。——《庄子·外物》