A psychological condition where mental/psychological pain, suffering, or distress isn't felt. Related to analgesia and anhedonia. In the most extreme cases of amensgonia a person could be constantly happy or in a constant state of mental neutrality.
Ex. "Rachel is such a nice girl, but she hardly ever seems unhappy about anything."
"Well, she might have amensgonia, she might not feel any mental pain at all."
Bro 1: hey dude, so did you end up getting Jenny pregnant last month?
Bro 2: nahh dude, apparently my mom gave me a vasectomy in my sleep when i was 12! #amcas