There is not one good thing to be said about regret. If it led to reformation, that might be something, but it does not. Regret is a tool of the devil to snuff out one's light, to absorb into self.
It makes one feel bad AND prevents one from being a help to one's neighbor. This is good reason for the Bible statement: "God requireth that which is past."
The antidote for regret is gratitude. Expressing gratitude for every little thing, "acknowledging Him in all thy ways," leaves no room for devil-talk. Perhaps more than ever, watchfulness is required to notice and respond to the need of our fellow-man during the Christmas season.