swat.

maybe it's like mosquito bites.
if you don't notice it, it would slowly disappear after a while, on its own.
but if you happen to see it, touch it - there goes your peace. the damn thing will itch and itch, and you'll scratch and scratch, until something else comes along to distract you.

then you'd forget, and the itch, it gradually goes away. until the next mosquito lands lightly on your skin...