Which idea is conveyed by this part of the extended metaphor that is created throughout the poem? Because a choice will take us in certain directions, it is not always possible to know what might have been.
If one choice does not work out the way it was intended, it is always possible to go back and change things.
Once a decision has been made, one should never look back and wonder what could have been different.
When torn between two decisions, it is best to remember that one can always go back and make a different choice.