I've had really good days and then all of a sudden terrible days... I can see that the 'good days' will become longer and longer and eventually the door will close.
When I have bad days, I noticed that something will trigger the horrible feeling and from there everything seems to be bad for a few days... but when I think about it, most is 'bad' bc of my mood from the trigger and how I see/react feeling that way, it's not that there has been much change in my surroundings.
Yesterday something snapped me out of it and I'm doing quite well again.
It helps me better if I set a goal for whatever I'm doing... gives me a positive feeling.