This poem is about choices, decisions and their consequences. It is a fact that once the choice has been made, there is no going back. The traveller standing on the road of life is confronted with a dilemma when both the paths or choices look equally promising. Once a road is chosen, the traveller has to move on.
There is no rewinding. There would never be a befitting time or opportunity for coming back and exercising the choice again. Time has changed, so has the psychology of the traveller. It will never be the same again. So one sticks to the road one has taken and makes it lead to the destination already decided.