expression
in for a penny, in for a pound; having gone too far to turn back
Idiomatic expression used when one is already committed to a course of action and might as well see it through, even if it becomes difficult. Literally 'a ship one has already boarded'.
もうここまで来たら乗りかかった船だ。最後までやろう。
We've come this far; we're in for a penny, in for a pound. Let's see it through to the end.
乗りかかった船だから、このプロジェクトを途中でやめるわけにはいかない。
Since we've already committed, we can't just abandon this project halfway.