@shermananski- I have 12 years experience with PTSD caused by the same time frame of having my 2nd, 3rd and 4th lung cancers. When I am depressed the last thing that I can do is to think positively. It's a contradiction of terms. Earlier this year Harvard Medical School upgraded a much earlier article about the causes of depression. The point of the article is that things are much more complex than once thought. It's far from not having enough of one chemical and too much of another. It's a long hard journey, but one well worth making. I am still on mine and may never stop.
whttps://www.health.harvard.edu/mind-and-mood/what-causes-depression

In order to think positively we all need to deal with ( to take the action that is necessary) the things that are making us depressed. Medications help with symptoms but not the cause. Making lists of what you can change now, or have power over and those that you don't can help weed out things that might be draining our energy. It's first and most importantly time to weed out the riff raff. Once the list with the "no power over" is put away it's time to deal with those that you do have power over. By power I mean the ability to change the way you react and look at things. You can change how they effect you. Usually, but not always those things that make us depressed have happened in the past. Time has changed our perceptions of them. Of course they happened, I'm not saying that they aren't. We can't change the past but we can put into perspective why they are still effecting us why do we still let them? Why do we help them stay and beat us up? This is a different time and out memories aren't perfect.

My mother had a huge influence over me. She was not a particularly warm woman and really had no idea how to emotionally be supportive. She expected great things without the teachings of how to go about them. We fought like cats and dogs and I gave her a run for her money most of my life with her. She was an artist of sorts and left many of her sculptures for her three children. Anyway, I put as many of her sculptures around my house as I could. I surrounded myself with her. Instead of really mourning and letting my nasty memories of her vanish I stayed angry and more and more depressed because those art pieces were a continuous reminder of her coldness and demeaning words. I entered therapy and one of things that I learned was that those pieces of art were a constant reminder of her and subconsciously I kept thinking of our conversations and fights and didn't let her go. Some of these will always make me angry when I think of them but by packing away most of her art I have also packed away some of the triggers that have begun a lot of my depressive thoughts.

Most of us have different stories but something triggers the memories and keeps us captive. Also, and I'm sure that you are aware of this, by doing negative things to yourself you reinforce any negative feelings that you have about yourself. By changing these things will be the first line of getting you feeling better and getting out of the house and will give you more power over them. Actions are what lead us to think positively. Does this make sense?