This definition — one of many — of a depression, of a physical place, comes with many synonyms: indentation, dent, cavity, dip, pit, hole, trough, crater. Their commonality? A location and a displacement. If something is sunken, then what was there is there no longer. A hole is an absence: it’s less than a whole. I picture an evaporated lake, or the overgrown and barely noticeable craters (the result of a dramatic impact) left by shells in Vietnam.
It makes sense that the most-used term for a low state of mind is also depression. When you’re in that sunken place, you know you’re lacking. You know that you were once happy, but that cheerful substance has been displaced. And you certainly feel lacking as a human being: enjoying a standard of living far better than most of the world, but barely able to drag yourself out of bed.
But maybe thinking about depression as a specific location can help with the healing. If it’s a place, you can compartmentalize. You could change the pejorative nature: maybe the hole becomes a safe place that protects you. Or a cozy nest where you can curl up and sleep things off. Maybe you can visualize climbing out of it, or slowly form it in your mind as a very shallow and barely noticeable indentation. You could list the gifts a depression leaves: fossils, salt — maybe a spring? The crater could fill with water and become a pond.