101
Brainwashing
(beehaw.org)
Realizing that not every moment in life will be deep, or meaningful, or vibrating with energy that would give him the fulfillment that he'd always hoped for, Todd unloaded the dishwasher.
being happy without external stimuli is called a Droud and it's a terrifying concept.
https://en.wikipedia.org/wiki/Wirehead_(science_fiction)
Directly triggering the brains rewardcentre with a device. I would definitely call that an external stimulus. But that depends on whether you use a literal or figurative meaning of the word 'external'.