My ADD leaves my open to get depressed over stuff fairly easy. Stupid stuff.
After the fact I can realize just how stupid it is but during really sucks.
It's likely that what you experience is a reaction to a number of quite specific stimuli. If you can find them out you can build methods of dealing with them very effectively.
Build a habit of doing things in a way of not exposing yourself to the triggers.
If this fails, stop the trigger, before doing anything.
Schedule actual cool down periods when triggered, where you actively cool down and acknowledge that all it takes is time.
Just something to consider. It doesn't have to work for you, but it might as well.