On a symbolic level, what do you think “the great harvest” is that the speaker once valued in "After Apple-Picking Time."
Frost speaks of fatigue, the end of the season tiredness after having picked so many apples.
For I have had too much
Of apple-picking: I am overtired
Of the great harvest I myself desired
The poem gives the impression of starting the season with high hopes, fresh energy, but as his point of view is after the harvest is done, he's readily sick of apples. As for the "Great harvest" it could easily be the money he was going to make - his harvest essentially - from the apple picking. At the end of the season even the money can't motivate him anymore.
On the symbolic level, I think that the "great harvest" that the speaker once valued is not money but is, instead, all of the "earthly" things that people want in life. Money could surely be one of them, but so would fame and accomplishments and possessions (or even the pursuit of great poetry, if you see Frost as the speaker).
On the symbolic or figurative level, you can argue, this is a poem about a man who has lived a long life and is now preparing himself for death. He is realizing that the things he worked so hard for are not necessarily what was important.