Our speaker is a very conflicted guy. He doesn't tell us too much about himself, but we know that he is facing a big decision; the road he's walking on, and the life he's leading, is splitting into two separate roads up ahead. Leaves are falling and the woods are yellow, so, if the woods are a metaphor for the speaker's life, we can guess that he's somewhere in the fall of his life, maybe his forties or fifties. In this stage of his life, it's probably too late to go back and change his mind after he makes big decisions; he knows that he probably will never have time.
The decision he's up against could be something like changing careers or moving to a different place. He could just be having the typical mid-life crisis, unsure if he likes where his life is going, even though he always thought he would. Whatever the decision is, it must be major, because he knows that he'll still be talking about it far in the future, saying that it made a big difference in his life.
We can guess that he likes nature, because he's out in the woods, just wandering around without a plan of where to go next. We know he's adventurous and impulsive, because though he spends a long time contemplating one path, he takes the other in a split second. He prefers to think that the path he takes is less traveled, even though both paths are about the same, and thinks that, in the future, he'll say that he took the path less traveled no matter what.
We're not sure if our speaker is happy or sad with the choice he's made. What do you think? He might not know either.