In this poem, he has had a hard day of apple-picking, and at the end of it, he is physically tired. The readers states, "I am drowsing off," and "I am overtired." In thinking about the day he has just had, he describes some other physical aspects of apple-picking. For example, "my instep arch not only keeps the ache," referring to the arch of his foot that is aching from standing on the ladder. As he is sitting there, he is achingly tired, but is having troubles falling asleep because the day keeps running through is head. Images of apples keep flashing in his mind and he says that "one can see what will trouble this sleep of mine." So, his feet are aching, he is exhausted and tired, but having trouble sleeping.
Mentally, he is tired too. He started off the day of picking with excitement for "the great harvest I myself desired," but is now exhausted and wanting to rest. But, his mind is restless, and can't get images and thoughts from the day out of his mind. He "cannot rub the strangeness" from his thoughts of the sheet of glass he lifted off of the water barrel that morning, the "rumbling sound of load on load of apples" being poured in the barrels, the "ten thousand fruit to touch." All of these things play over and over in his mind and it won't let him rest.
So, he is physically and mentally tired, but unable to quite let go of the day and sink into blissful rest. I hope that helps. I also provided links to some explanations of the poem that are useful. Good luck.