A sense of finality and irreversibility. It sounds like you might be referencing a situation where someone makes a serious commitment or decision, and it has significant consequences that can't be undone.

In some cases, this phrase could be related to:

1. **Marriage**: The idea is that once you're married, there's no "going back" in the sense of undoing the union.

2. **Business deals**: Signing a contract or making an agreement might mean locking yourself into a certain course of action that can't be easily reversed.

3. **Personal growth**: Reaching a point where you've made significant changes to your life, such as quitting a job or ending a relationship, and it's not possible to go back to the way things were before.

Which context do you think this phrase fits best? Or is there something else I'm missing?