autopilot
noun
°A mechanical, electrical, or hydraulic system used to guide a vehicle without assistance from a human being.
"I set the autopilot to due south, so I could get some rest."
°A state of mind where one no longer thinks about doing his actions, he just does them seemingly as a second nature.
"I've been doing this 12 hours non-stop, and am so hungry and tired that I've stopped thinking, I'm now on autopilot."