13 surprising reasons you’re always dog tired – and what to do about it | Sleep | The Guardian

While you sleep, your brain is putting in a shift. Dr Jemma King provides an analogy: “Imagine all the events that happen during the day get documented and put into a manila folder that’s stacked on the desk of your personal librarian, who works through the night, deciding what to keep and what to discard. Usually this happens smoothly, but sometimes folders need the boss to decide, and you’ll be woken at 3am with a burning thought that makes you feel stressed. The stress hormone cortisol has a half-life of at least 30 minutes, so if you engage with that thought, you have at least until 3.30am before your stress levels go back to a ‘sleep-permissive’ level.”
— Read on www.theguardian.com/lifeandstyle/2026/jul/24/reasons-you-feel-tired-what-to-do-about-it-fibre-creatine