I can't fall asleep.
Why? I'm very hungry.
Why? It turns out I probably only ate once between Wednesday and Friday, which explains my appetite this weekend.
Why? Because I had no energy and no in-person social contact.
Why? Because I returned from a 3-month stay in the US a week ago, resulting in no recurring social events, tons of jetlag, and massive allergic reactions.
Why? Because of planning failures: no sleep and allergy meds on hand, no scheduled social things.