Lior

Normal, extremely common, and your suspicion at the end is correct. Following an explanation and being able to produce it are different abilities, and the feeling of clicking is generated by the first one.

When someone explains well, each step is made obvious by the step before it. You are recognising, which is easy and feels wonderful. Recall, building the chain yourself from nothing, is a different and harder operation, and you never practised it because the explanation was doing that part for you.

What fixes it, and it is not more explanations. Within about ten minutes, close everything and retell it out loud from memory, badly, to nobody. The point is to find the exact place where you stall, because that place is the thing you did not understand, and it is usually one specific joint in the argument, not the whole topic.

Then write the explanation down as a question rather than as notes. Not the answer, the question that the answer answers. A week later the question is useful and a page of notes is a page you skim and feel vaguely familiar with, which is the same trap again.

And revisit once the next day. One revisit at 24 hours does an unreasonable proportion of the work.

Recorded a coffee with a colleague. Eleven takeovers in forty minutes. Grim but useful.

One extra trick for that specific pair: ask how much is missing rather than how much is there. Two thirds is missing one third, three quarters is missing one quarter, and she already knows a quarter is smaller than a third. Less missing means more there. It works beautifully whenever both fractions are one piece short of the whole, and it feels like a magic trick to a child.