Napoleon compares his mind to a cupboard of drawers, each holding a subject or affair; he claims conscious control over attention by 'shutting' one drawer and 'opening' another to switch trains of thought, and achieving sleep by 'closing all the drawers.' The post presents this as a concise metaphor for deliberate mental management.
Napoleon uses a cupboard metaphor: different subjects and affairs are 'arranged in my head as in a cupboard' (quote).
Napoleon on How He Thinks:
"Different subjects and different affairs are arranged in my head as in a cupboard.
When I wish to interrupt one train of thought, I shut that drawer and open another.
Do I wish to sleep?
I simply close all the drawers, and there I am – asleep."