A beach, an airport, a rest stop, a graveyard, an outlet mall bathroom: These are a few of the places where the dancer Marlee Grace has filmed herself improvising during the past two years. Ms. Grace, 29, is the artist behind the Instagram account Personal Practice, a trove of short videos documenting her daily movement practice, and the author of a new self-published book about the project, “A Sacred Shift.” A scroll through the hundreds of posts reveals videos of her jamming out next to a post office; weathering the snow and rain; and, perhaps most often, dancing in her living room. Marlee is dedicated to: self-forgiveness and she uses dancing as a means of exploring and sharing this invaluable, vulnerable practice of letting go.