In the poem’s second line, the speaker expresses his regret that “he could not travel both” roads, being just one traveler. In the third stanza, he exclaims,

Oh, I kept the first for another day!
Yet knowing how way leads on to way,
I doubted if I should ever come back.

Because one road (or one decision) tends to lead to another, then another, and so on, people are often unable to go back to the original decision point and make a different choice. The permanence of decisions is a function of time’s linearity, which, in turn, makes the road a particularly apt metaphor for the experience of life. The roads we travel—the decisions we make—change us and lead to unexpected possibilities, perhaps, that prevent us from returning to the places we used to live and the selves we used to be.