The feeling one gets when they empty out the spit valve of their musical instrument (a trumpet or trombone, for example) and find that spit is not the only thing that is coming out. The realization that someone has taken it upon themselves to jerk off onto the mouthpiece and into the instrument comes quickly. The accompanying feelings that the person has include (in this order) disbelief, extreme sorrow, rage, hate for the whole world, fear, pity, nausea and other phsycial sickness, and finally self hatred. The self loathing heaves are a thing that many people don't even wish on their worst enemy.
After a long day of enforcing city health codes, Hansel decided to jam out for a while. He grabbed his trumpet and began belting out some songs. He emptied out the spit valve and his life took a considerable turn for the worse. As soon as he figured out someone had given him a "gift", he immediately got the self loathing heaves. He cried himself to sleep that night.