There's a kind of narcissism in depression. A point at which a person goes from the experience of feeling bad, to where they simply are bad. And at that point, the depressed mind can only access experiences that reinforce the depression. The disease of it is almost beautiful from the outside, for how well its designed to be impenetrable and self-sustaining. Its easy to treat if you can break the skin of it, and yet so hard to suffer.
As a clinician, its the hardest and the easiest thing all at the same time, because it creates its own universe and you can't engage it until the patient lets you into their world and trusts you enough to travel with you back to yours. So there's 2 points (among many) for the clinician: 1) allowing yourself to be present in the patient's subjective reality of the badness and pain, and 2) having a (less distorted) world to bring them back into that is genuine, functional, and not deceptive or fake. A good therapist knows that the therapy doesn't make you feel better, it makes you *feel more.
*the idea being that one learns to self soothe along the way. if you can get through the feelings you don't have to distort the world to avoid them.