To answer the second part of your post "Have you ever managed to get out of this state by making a conscious decision?"
Yes I have managed to reduce the depression by avoiding things that require a lot of complex thinking.
Just like when you are running low on fuel in your car , you reduce your use of the accelerator.
The depressing thoughts that I get are a result of low serotonin and i know this because I was on medication which fixed me for a while. During this time my depressing thoughts and behavior disappeared. My mind worked extremely well. Unfortunately over the next 10 years it stopped working.
One major thing I learned is to slow down everything you do it saves serotonin.
RE: Questions to ask yourself on procrastination