French has a lot of idioms related to food that you should take time to learn.
Les carottes sont cuites is one interesting French idiom that literally translates to "the carrots are cooked".
Depending on the context used, les carottes sont cuites means that a situation is settled or decided, and there's nothing more that can be done about it. Basically, it means "it's all over" or "the goose is cooked".
You can't uncook carrots, so the phrase implies that a certain outcome is irreversible or inevitable at this point.
If you don't want to use les carottes sont cuites, here are two alternatives:
French idioms are a colorful way to express ideas and feelings, and they often don't translate well. Understanding them often requires knowledge of the language and the culture in which they're used.