When you’re so deep in the work that you forget to check your phone, that’s the zone. Protect it like treasure.

That state takes a while to enter and almost no time to leave, which is the whole trouble with it. It is produced less by discipline than by an uninterrupted stretch long enough for your attention to sink, and a single interruption resets the clock rather than pausing it. Recognising it when it arrives is most of the skill.

Guard the conditions rather than the feeling. Block out a stretch where nothing is expected of you, and when you notice you are inside it, do not stop to mark the occasion.