The two roads can really stand in for any two choices or possibilities, including two different ways of life. Just as the speaker considers the two roads before him, he might consider two possible life paths which are open to him at a particular moment in time. He claims that the second option is "just as fair" as the first, just as two possible ways of life might seem equally appealing (line 6). Further, he says, "[...] the passing there / Had worn them really about the same" (9-10). He means, here, that an approximately equal number of people have chosen each path, just as many numbers of people will have taken each of the ways of life which are open to us. After the speaker chooses the second path, he engages in some wishful thinking, that someday he might return to that first path and see where it leads, but, he says, "knowing how way leads on to way, / I doubted if I should ever come back" (14-15). Once one chooses a particular way of life, one cannot really switch gears and suddenly choose a different one, or, at least, it's extremely difficult to do so.