Think about regret as if it were sin. Some regrets are mild, but acute. The regret associated with choosing the wrong supermarket checkout lane, or buying an outfit that you notice goes on sale the next week—these seem woeful. They chafe, but their pains are pin pricks that soon subside. These are venial regrets.
Regret is more severe when it steeps in sorrow rather than in misadventure, when it becomes chronic—mortal rather than venial. But counter-intuitively, mortal regrets are less noticeable than venial ones, because they burn slow and low instead of hot and fast: the regret of overwork and its deleterious effects on family. The regret of sloth in the face of opportunity. The regret of acquiescence to one’s own temperament.
Mortal regrets are tender, and touched inadvertently they explode with affective shrapnel. Venial regrets shout, “alas!” but mortal regrets whisper, “if only.”
Source: The Atlantic