When action grows unprofitable, gather information; when information grows unprofitable, sleep. – Ursula K. LeGuin
And take naps. I keep a couple of pillows and a mat here in my office and don’t hesitate to grab naps whenever I can… either 5 minute ones or sometimes over an hour. I like to get up early and work/write after about 6 hours of sleep, which is not quite enough to get me through the day. I’m always waaaay more refreshed and full of ideas afterwards.