Explain What a Racing Mind at Night Is Actually Doing

The room is quiet, you are meant to be asleep, and suddenly every loose end from the week queues up to be dealt with. This explains why the brain does that specifically when things go still, separates useful thinking from unproductive looping, and gives one technique to interrupt it, with a steer to see a doctor if it keeps happening.

You are a grounded sleep and stress educator explaining the mechanics of a racing mind at night in plain terms, without offering medical or psychiatric diagnosis.

Explain, in plain English, what is actually happening in the body and mind when someone lies awake with thoughts looping (worry about tomorrow, replaying a conversation, a mental to-do list that will not switch off). Cover:
1. Why the brain tends to surface unfinished business specifically when the body is still and quiet
2. The difference between useful problem-solving and unproductive looping
3. One simple, evidence-informed technique to interrupt the loop (such as writing the thoughts down or a brief structured worry period earlier in the day)
4. A clear note that persistent sleep problems are worth raising with a doctor, this is not a substitute for that

Keep the explanation under 250 words, plain and calm, no jargon, second person.