What's the meaning of "How'd you manage that"?

Question

Could you please tell me what the relationship is between the phrase:

"How'd you manage that?"

and the next sentences:

"I felt stupid. I should have been able to do it, I thought. It’s a simple thing."

Here is the full text:

My back struck iron: the trailer’s wall. My feet snapped over my head and I continued my graceless plunge to the ground. The first fall was seven or eight feet, the second perhaps ten. I was relieved to taste dirt. I lay on my back for perhaps fifteen seconds before the engine growled to silence and I heard Dad’s heavy step. “What happened?” he said, kneeling next to me. “I fell out,” I wheezed. The wind had been knocked out of me, and there was a powerful throbbing in my back, as if I’d been cut in two. “How’d you manage that?” Dad said. His tone was sympathetic but disappointed. I felt stupid. I should have been able to do it, I thought. It’s a simple thing.

Answer 1

The father asks how the speaker managed to fall, implying that falling would have been something difficult or out of the ordinary to do under the circumstances. When the speaker says that the father looked disappointed he is recognizing that the father thinks it was a mistake to fall. The speaker then agrees with the father. He also feels that he shouldn't have fallen. He should have been able to 'do it', meaning he should have been able to finish whatever he was doing before the fall.

Answer 2

The phrase itself (or any variant of it, such as, "How did you manage to do that?" or, "How did you pull that off?") expresses astonishment that someone was able to do something surprising. The question is essentially asking, "How did you do that?" but with an added sense of surprise.

For example, I might tell you that I once got 11 passengers in my compact car and drove them somewhere. You might say, "How'd you manage that?"

In this context, though, the father is surprised that the son ended up doing something so clumsy. Perhaps he thought his son should have been more cautious. When used in a context like this, there is a certain amount of sarcasm involved. It's like the dad is asking:

How in the world did you end up doing something that clumsy?

Answer 3

How'd you manage that? means:

How did you manage that? It is a contracted form, used in speech or heard in speech.

To manage [to do] something: be able to do it; to happen to do something.

That kind of comment is typical of parents to children. The son had hurt himself because he did something stupid.