You're genuinely, physically e.x.h.a.u.s.t.e.d. You're totally run off your feet and find yourself frequently fantasising about being horizontal. Even just the thought alone of doing anything other than collapsing when you get home makes you feel tired. You get through the day with a little help from the sugary snack department and plenty of strong coffee.
Your body is crying out for some good ol' classic physical rest. Time to listen to the calling to be horizontal!
If this is unachievable, micro-naps of 15-30 minutes work wonders.
It may seem contradictory but regular breaks from work to stretch and have a shake about can oxygenate the body and provide you with more energy.
3) Switch it up.
Relaxing in a Pearpod chair can break up the day and transport you away from your work for a few moments, leaving you feeling refreshed.