We discover sentiment-driven equilibria in popular models of imperfect risk sharing. In these equilibria, sentiment dynamics behave like uncertainty shocks, in the sense that self-fulfilled beliefs about volatility drive aggregate fluctuations. Because such fluctuations can be detached from the wealth distribution, rational sentiment helps resolve two puzzles that plague models emphasizing financial sector balance sheets: (i) financial crises emerge suddenly, featuring large volatility spikes and asset-price declines; (ii) asset-price booms, with below-average risk premia, predict busts and financial crises. Methodologically, our contribution is using stochastic stability theory to establish existence of sunspot equilibria.