When I felt tired, I would go for a walk, knowing that I needed to inject some fresh air (as fresh as Zone One in London can get) and not allow myself to sleepily carry on at half speed. This could be just ten minutes, but it always made a noticeable difference, and I do it all the time now. I walk in the mornings before I even have a cup of coffee. It gives me space between deep sleep and the busy day, time to fully let my brain wake up, so I don’t jolt it into panic with a rush to the Tube or by expecting to start work straight away.
