To exhibit a conspicuous (sometimes malevolent) pleasure or sense of self-satisfaction, often at an adversary's misfortune.
To triumph, crow, relish, glory, revel.
An act or instance of gloating.
To feel sorry about (any thing).
To feel sorry about (a thing that has or has not happened), afterthink: to wish that a thing had not happened, that something else had happened instead.
Emotional pain on account of something done or experienced in the past, with a wish that it had been different; a looking back with dissatisfaction or with longing.
The amount of avoidable loss that results from choosing the wrong action.