I will discuss the applicability of concepts from classical soft matter physics to the problem of slow relaxation and non-ergodicity in quantum many-body systems. Soft materials which display slow cooperative dynamics such as glasses often do so as a consequence, not of quenched disorder, but of effective dynamical constraints. These give rise to metastability, spatially fluctuating relaxation and eventual arrest. I will consider how analogous concepts may be useful when thinking about slow dynamics, metastability and non-equilibrium in quantum systems, connecting to the question of many-body localisation in the absence of disorder and to the fate of MBL in the presence of dissipation.