How an interacting many-particle system prepared in an initial state which is far from equilibrium evolves in time, and how it thermalizes if at all, is an important and open question which is also of experimental relevance. In this talk I will consider a system of interacting bosons that are initially out of equilibrium due to an interaction quench. I will study the stability of this nonequilibrium system to a periodic potential, and in particular show that even though the system is isolated from the surroundings, it can act as its own reservoir, with a self-generated dissipation and an effective-temperature leading to quasi-thermal behavior at low frequencies and long wavelengths. I will also compare this with results for the steady state behavior of nonequilibrium and weakly interacting fermions.