The only thing to do is to treat each shift as a one-time-only emergency: you've got fifty starving people out there, lying scattered on the battlefield, so get out there and feed them! Forget that you will have to do this again tomorrow, forget that you will have to be alert enough to dodge the drunks on the drive home tonight—just burn, burn, burn! Ideally, at some point you enter what servers call a “rhythm” and psychologists term a “flow state,” where signals pass from the sense organs directly to the muscles, bypassing the cerebral cortex, and a Zen-like emptiness sets in.