Remorse following the act of flatulating. Cause can be various. E.g., one tries to flatulate but soils one's underwear as well (see shart); one's flatus turns out to have an unexpectedly unpleasant quality (usually strength or abundance); (most common) an attractive person approaches after one has flatulated, leading to panic and lost opportunities for flirtation and/or sex.
The boys had fun horsing around in the car on the freeway until one of them sharted. There was nowhere to stop. Their laughter died out and postfartum depression kicked in.