冇咁大個頭就唔好戴咁大頂帽 [－－－个头－－－－－－顶－]

Jyutping mou5 gam3 daai6 go3 tau4 zau6 m4 hou2 daai3 gam3 daai6 deng2 mou2
Pinyin mǎo hán dà gè tóu jiù wú hǎo dài hán dà dǐng mào

Definitions (粵典–words.hk)
  1. 語句
    叫​人​唔​好​不自量力​嘅​用​語
    an instruction to someone not to overreach themselves, not to take on more than they can cope with, "don't bite off more than you can chew!"; literally: without a big head, don't wear such a big hat