The author comes across a split in the road and is very indecisive on which path he should take.
In the morning, the author looks at the two again and determines they are both fairly equal and nobody had walked on either that day yet.
The author decides to just take the second path on a whim just to see what it's like and forget the indecisiveness he had.
The author realizes even if he wanted to come back to go the other, paths lead to more paths and he will probably not be able to.
The author looks back on his decision and what he will tell others in the same position in the future.
The theme of TRNT is decisions and how very little ones can make extremely terrible changes. This relates to the 25% of highschool freshmen that drop-out. These drop-outs commit 75% of crime and are much less likely to be hired.