The phrase "with a sigh" is deliberately ambiguous as to it being a positive or negative judgement, because his past self, looking forward to the sigh, knows the decision may ultimately be seen as significant (hence the sigh), but doesn't yet know whether it will be regretted or the opposite.
By the final line, that his choice "has made all the difference", he means that although he knows not, before or …show more content…
Another important aspect of the poem is that he is contemplating how a fairly random decision, for an irrelevant reason, can lead one down a completely different path, permanently changing one's life. He takes the less worn road, but the difference in wear was so marginal that by his own taking the less worn one, they were worn roughly the same. What he means is that his reason for choice had little basis and was very marginal, thus he's contrasting the marginality of the choice with the enormity of the consequences. He's contemplating effectively, the butterfly effect. Finally, by taking the road less traveled there may be a hint at an overall philosophy in life of not following the crowd.
The true beauty of this poem for me, and what makes it so enigmatic, is the mutual recognition in a person, between two moments past and future, of one's frame of mind at the other moment. We are so long in time, that such connections are very, very rare, and to have a moment of empathy with one's future or past self is both to gain a momentary insight into the nature of life and aging, and to momentarily gain a new internal context to how we perceive the aging of others, and what it really means to