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.

wiedzieć, gdzie leży jego interes, wiedzieć, skąd czerpie korzyści

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.
Zawsze pomaga swojemu szefowi, bo wie, gdzie leży jego interes.
You need to know which side your bread is buttered on if you want to succeed in this company.
Musisz wiedzieć, gdzie leży twój interes, jeśli chcesz odnieść sukces w tej firmie.