To pluck is to pick or pull a single item out of many, like a flower or a hair. As a noun, pluck is energy or enthusiasm, even when things are looking grim.
Don't pluck only the best cherries off the tree: that's cherry-picking! Before you cook a goose, you need to pluck its feathers. If it looks like your goose is cooked, however, then show some pluck, and figure out a way to save yourself. Some characters who are famous for showing pluck include the Artful Dodger, Little Orphan Annie, and Benji the dog. They all kept their chins up and kept on trying, even when things looked really dark.