Depression can come from a variety of things and the core or the root of depression should be tackled. However, these are some things that will help get you out of a rut in general, extending beyond finding a solution to your core problem.
Have/Create a New Routine
Depression can tear away your old (good) habits and make your life staggered and unstructured. Get back on track by recreating this structure or change things up if you feel your current routine is drab or dragging you down.