idiom · to console oneself with illusions or false hopes when the reality is unavailable

他买不起昂贵的相机，只能每天看说明书望梅止渴。

idiom · to quench one's thirst by thinking of plums (original idiom meaning)

曹操利用望梅止渴的计策，带领士兵们走出了荒漠。