This paper extends the benchmark New-Keynesian model by introducing two frictions: (i) agent heterogeneity with incomplete markets, uninsurable idiosyncratic risk, and occasionally-binding borrowing constraints; and (ii) bounded rationality in the form of level-k thinking. Compared to the benchmark model, we show that the interaction of these two frictions leads to a powerful mitigation of the effects of monetary policy, which is more pronounced at long horizons, and offers a potential rationalization of the “forward guidance puzzle.” Each of these frictions, in isolation, would lead to no or much smaller departures from the benchmark model. (JEL D52, D81, E12, E52)