I work in arbitrary blocks but analyze: what's my optimal session? Map work sessions: length, quality over time, fatigue point. Calculate: my focus capacity vs. session length vs. quality decline. Show me my session length: I'm productive for this long, then decline. Give me the optimal session: work this long, break, repeat. Include: what my natural focus span is, whether I'm working too long or too short, and what session length optimizes quality.