You can't go through life looking down on everyone; you have to learn to respect others.
Tips
history
Comes from Li Ruzhen's Qing-dynasty novel 《镜花缘》(Flowers in the Mirror, ch. 52): '但他恃著自己学问，目空一切' — 'relying on his own learning, he held everyone in contempt'. Always negative.
memory
Literal breakdown: 目 'eye' + 空 'empty / nothing' + 一切 'everything' = 'in his eyes, everything is empty / nothing'. Picture someone whose eyes look right through every other person in the room.
