"Juan Mode" is derived from the difficulty setting "Kid Mode" from the Nintendo Gamecube game "Viewtiful Joe." Kid Mode, and subsequently Juan Mode, imply a lackluster difficulty for gaming and life in general.
Juan Mode is used to describe activities such as blowing off people, places, things, events, for the selfish, instant gratification of ones self. Examples of this include calling out of work to quest, arranging schedule to quest and/or game, "working" from home while logged into World of Warcraft and questing all day, sleeping in late when working from home, not showering, not brushing teeth - just walking from said bed to downstairs, prepping laptop, and logging in.
Juan: Well, we got two inches of snow, (in 38 degree North Carolina Weather) so we get to work from home today.
Matt: Wow, turning Juan Mode on, eh? You logged in yet?
Juan: Well, I don't even care what you guys say; now activating Juan Mode and LOGGING IN.