ukr.vitalinguist — How to say it in authentic Ukrainian

assert yourself
C2 verb — assert yourself

to behave or speak in a strong, confident way

Bilingual dictionary attestations (1 dicts, 1 rows)

Українсько-англійський словник
ка́чуть , who makes himself a sheep, will be eaten by the wolf, or if you don’t assert yourself , you will be pounced on.

Live source: https://e2u.org.ua/s?w=assert%20yourself&highlight=on