We offer a novel argument for one-boxing in Newcomb's Problem. The intentional states of a rational person are psychologically coherent across time, and rational decisions are made against this backdrop. We compare this coherence constraint with a golf swing, which to be effective must include a follow-through after the ball is in flight. Decisions, like golf swings, are extended processes, and their coherence with other psychological states of a player in the Newcomb scenario links her choice with the way she is predicted in a common cause structure. As a result, the standard argument for two-boxing is mistaken