know which side your bread is buttered on

US /noʊ wɪtʃ saɪd jʊər brɛd ɪz ˈbʌtərd ɑn/
UK /noʊ wɪtʃ saɪd jʊər brɛd ɪz ˈbʌtərd ɑn/
"know which side your bread is buttered on" picture
1.

saber de que lado o pão está untado, saber onde está o seu benefício

to be aware of where your advantages or benefits come from and to act in a way that maintains them

:
He always helps his boss because he knows which side his bread is buttered on.
Ele sempre ajuda o chefe porque sabe de que lado o pão está untado.
You need to know which side your bread is buttered on if you want to succeed in this company.
Você precisa saber de que lado o pão está untado se quiser ter sucesso nesta empresa.