In Robert Frost's "After Apple-Picking" why does the narrator refer repeatedly to sleep?

This brilliantly allegorical poem presents us with a man who is
exhausted after working long and hard picking apples. As he contemplates the dream he expects to
have, he recalls the details of picking apples. He recalls the rungs of the ladder that he
climbed to pick apples, the smell of them, and the sound of the wagons carrying their apples into
the barn. However, less pleasantly, he realises that he has had enough of apple picking and now
finds the bountiful harvest that he had once wanted to be excessive. Likewise, just before he
falls asleep he thinks about the fallen apples that had to be taken away to the cider mill. He
feels his sleep will be troubled more by these failures than by his successes. The poem ends with
the poet's ignorance about what kind of sleep he will enter in to: it may be a form of
hibernation or death.

Sleep is something that is used symbolically
in other Frost poems, such as "Stopping by Woods on a Snowy Evening," to refer to death. Many
critics see this poem as an allegory about the art of poetry and being a poet. The speaker has
wished for a successful poetic career and has many poems that have been successes. However, now,
looking back, he sees how this career has made him completely exhausted. He doesn't want anything
else to do with it. He feels his "sleep" will be dominated by the failures, the "apples" or ideas
that he started but never finished, then by his successes. Lastly, he is concerned about the
state of sleep he will enter, and Frost explores different attitudes towards what lies beyond our
death. Will it be a kind of hibernation, where we stay asleep for a time and wake up into a
different world? Or will it be an ending rather than something that heralds a new beginning?
Either way, sleep is focussed on so much because it is what the speaker desires and wants now, as
he is so tired after his toil.