It’s possible to temporarily ‘trick’ your brain into a short additional period of active attention if you’re feeling sluggish and inactive. To do this, you need to jolt your brain into needing to feel its way around again. If you’re working on a long report, move to a new part of the room every half an hour or so. If you’re working on an Excel spreadsheet, change all the fonts to red and green just for half an hour and then change it all back. These tweaks in perspective can really help to keep you going that bit longer than you really have the energy for.