Regret in a dream commonly revisits a choice you're still judging yourself over -- a fork in the road you keep replaying, wondering what would have happened if you'd gone the other way. Facing that choice again in the dream can be an invitation to finally make peace with it, rather than a sign you need to reverse it.
'Tis ill to begin any lawsuits or other controversies when the Moon is ill dignified: the plaintiff without doubt will be overcome. - William Lilly (1602.-1681.)