The distance he was to go was regulated, not so much by his powers of endurance as by the various objects by the wayside--the lamp-posts, for instance.

During each rest he used to look ahead and select a certain lamp-post or street corner as the next stopping-place, and when he start again he used to make the most strenuous and desperate efforts to reach it.
Generally the goal he selected was too distant, for he usually overestimated his strength, and whenever he was forced to give in he ran the truck against the kerb and stood there panting for breath and feeling profoundly disappointed at his failure.
On the present occasion, during one of these rests, it flashed upon him that he was being a very long time: he would have to buck up or he would get into a row: he was not even half-way up the road yet! Selecting a distant lamp-post, he determined to reach it before resting again.
The cart had a single shaft with a cross-piece at the end, forming the handle: he gripped this fiercely with both hands and, placing his chest against it, with a mighty effort he pushed the cart before him.
It seemed to get heavier and heavier every foot of the way.

His whole body, but especially the thighs and calves of his legs, pained terribly, but still he strained and struggled and said to himself that he would not give in until he reached the lamp-post.
Finding that the handle hurt his chest, he lowered it to his waist, but that being even more painful he raised it again to his chest, and struggled savagely on, panting for breath and with his heart beating wildly.
The cart became heavier and heavier.

After a while it seemed to the boy as if there were someone at the front of it trying to push him back down the hill.

This was such a funny idea that for a moment he felt inclined to laugh, but the inclination went almost as soon as it came and was replaced by the dread that he would not be able to hold out long enough to reach the lamp-post, after all.