Thoreau captures so perfectly the philosophy inherent within the changing of the seasons. From his journal, here he elucidates a sense of urgency that rings true as I enter my 43rd August.

What means this sense of lateness that so comes over one now,–as if the rest of the year were down-hill, and if we had not performed anything before, we should not now? The season of flowers or of promise may be said to be over, and now is the season of fruits; but where is our fruit? The night of the year is approaching. What have we done with our talent? All nature prompts and reproves us. How early in the year it begins to be late! It matters not by how little we have fallen behind; it seems irretrievably late. The year is full of warnings of its shortness, as is life.