Unemotional apathy.
Unconcerned nonchalance.
The state of being indifferent.
Unbiased impartiality.
Self-identity defined through the negation of difference, non-difference.
A lack of enthusiasm.
The amount of avoidable loss that results from choosing the wrong action.
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.
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.
To feel sorry about (any thing).