We show that endogenous variation in risk aversion over the business cycle can jointly explain financial market responses to high-frequency monetary policy shocks with standard asset pricing moments. We newly integrate a work-horse New Keynesian model with countercyclical risk aversion via habit formation preferences. In the model, a surprise increase in the policy rate lowers consumption relative to habit, raising risk aversion. Endogenously time-varying risk aversion in the model is crucial to explain the large fall in the stock market, the cross-section of industry returns, and the increase in long-term bond yields in response to a surprise policy rate increase.