Psychological state is key, and I think you're understating it.

The human mind is always passively working on problems. We are not necessarily aware of how much working memory is "tied up" on background computations, but when it's a lot, we will feel a natural aversion to new learning, it will be exhausting, and we will lack for curiosity. This is fine, working as intended.

When in this state, what one usually needs to do is a different part of the learning process: not absorbing new information or abstractions, but making sense of what one already knows, working out contradictions, assembling larger-scale theories--synthesis, basically. "Learning" is only one part of the arc of "thinking".

Usually this is best done by writing, and usually comes easiest when trying to convince someone else or what we believe. If you can't find the energy to learn, try writing instead.