Взялся за гуж, не говори, что не дюж (Vzyalsya za guzh, ne govori, chto ne dyuzh)

Meaning: Once you've taken something on, don't complain that it's too hard.

Literally: Once you've taken the harness strap, don't say you're not strong enough

Example: “Ты сам вызвался руководить проектом. Взялся за гуж, не говори, что не дюж.” — You volunteered to lead the project yourself: in for a penny, in for a pound.

Equivalents in English, French, Spanish, Japanese, German, and 3 more languages

English: In for a penny, in for a pound
French: Quand le vin est tiré, il faut le boire (literally: When the wine is drawn, you must drink it)
Spanish: De perdidos, al río (literally: From lost, to the river)
Japanese: 毒を食らわば皿まで (Doku wo kurawaba sara made) (literally: If you eat poison, lick the plate too)
German: Wer A sagt, muss auch B sagen (literally: He who says A must also say B)
Portuguese: Perdido por cem, perdido por mil (literally: Lost for a hundred, lost for a thousand)
Dutch: Wie A zegt, moet ook B zeggen (literally: Whoever says A must also say B)
Polish: Jak się powiedziało A, trzeba powiedzieć B (literally: Once you've said A, you have to say B)