Why were people so unprepared for the global financial crisis, the European debt crisis, and the Fukushima nuclear accident? To address this question, we study a model in which agents make state-contingent plans - think about actions in different contingencies - subject to the constraint that agents can process only a limited amount of information. The model predicts that agents are unprepared in a state when the state has a low probability, the optimal action in that state is uncorrelated with the optimal action in normal times, and actions are strategic complements. We then compare the equilibrium allocation of attention to the efficient allocation of attention. We characterize analytically the conditions under which society would be better off if agents thought more carefully about optimal actions in rare events.