Gray Dog is an apt name of a not-full-blown depression. A good handle for the not-debilitating but not-feeling-good sadness that sucks away energy and joy.
Writing this piece was brave and, I am sure, exhausting. Keep writing. Write when you don’t want to and the words must be excavated like diamonds. Chip, chip away. Because your words are diamonds and because the act of mining them focuses your attention on something other than your unwelcome guest, depression.
Sadness wants all your attention, ever ounce of your energy. Be stingy. Give most of your awareness and energy to your writing. You’ll starve the bastard one word at a time. He’ll get hungry and bored and annoyed, and he’ll leave.