Momentum in thinking is real and it takes time to build. Once you are moving, ideas connect faster, the material stays loaded, and progress accelerates, which is why the last hour of a long session is often worth more than the first. Every interruption spends that accumulated momentum.

Think of a concentrated stretch as building something you will lose if you stop. Protect the tail end of a session rather than only the start. The compounding is what you are actually paying for with the discipline.