A vast range of neurophysiological, neuropsychological and behavioral results in monkeys and humans have shown that the immediate surroundings of the body, also known as peripersonal space (PPS), are processed in a unique way. Three roles have been ascribed to PPS mechanisms: to react to threats, to avoid obstacles, and to act on objects. However, in many circumstances, one does not wait for objects or agents to enter PPS to plan these behaviors. Typically, one has more chances to survive if one starts running away from the lion when one sees it in the distance than if it is a few steps away. PPS makes sense in shortsighted creatures but we are not such creatures. The crucial question is thus two-fold: (i) why are these adaptive processes triggered only at the last second, or even milliseconds? And (ii) what is their exact contribution, especially for defensive and navigational behaviors? Here we propose that PPS mechanisms correspond to a plan B, useful in unpredictable situations or when other anticipatory mechanisms have failed. Furthermore, we argue that there are energetic, cognitive and behavioral costs to PPS mechanisms, which explain why this plan B is triggered only at the last second.