I try 4-hour deep work blocks but analyze: is that actually my optimal duration? Map my focus capacity: when does quality drop, when do I get diminishing returns. Calculate: if my deep work quality peaks at 90 minutes, am I wasting time past that? Show me the personal focus curve: my optimal work duration. Give me the customized blocks: work this long, break, repeat. Include: what my actual focus capacity is vs. what I think it should be, whether forcing long sessions is counterproductive, and what my natural rhythm actually is.