Is there an English idiom for when you must commit to a course of action even if it turns out to be the wrong one?

Kind of like a "might as well go for it" kind of thing, in my language there are idioms that roughly translate to "you must finish everything on your plate, even if it's poison" or "you must follow the javelin you have hurled".

Solution 1:

Per Merriam-Webster:

in for a penny, in for a pound
idiom
British
—used to say that a person should finish what he or she has started to do even though it may be difficult or expensive
“If you want to quit, I'll understand.” “No, I'm sure we can do this. In for a penny, in for a pound.”

Solution 2:

the die is cast

You can say "the die is cast," which refers to one of the dice gamblers use in games of chance.

The meaning is, once the dice have left your hand, you have to play with whatever they show, even if bad.

Solution 3:

1. When someone complains that they are in a bad situation as a result of a decision they have made, or 2. when someone points out that the situation the other person is in is of their own making:

You have made your bed and now you must lie in it.

See The Free Dictionary.

Solution 4:

Bite the bullet

If someone bites the bullet, they accept that they have to do something unpleasant but necessary.

{journalism}

Tour operators may be forced to bite the bullet and cut prices.

[Collins]

Better yet,

Burn your boats

[British]

or Burn your bridges

To do something which forces you to continue with a particular course of action, and makes it impossible for you to return to an earlier situation

I didn't sell it because I didn't know how long I would be here. I didn't want to burn all my bridges.

[Collins]

Solution 5:

point of no return n. pl. points of no return

1. The point in a course of action beyond which reversal is not possible.
2. The point in the flight of an aircraft beyond which there is insufficient fuel for return to the starting point.

AHD