The one that's been working for me the last 2 years is ,when gloom descends , to remind myself that" life IS s**t" , that it's ( the awfulness) not just ME!! This works like a charm.
Since discovering am ASD also helps to remember that as a result of hard-wiring I keep expecting humans and human systems to be logical , when they are NOT. This helps me to touch down and be less freaked by all the thousands of illogicalities in each day!!
If I have the time and courage to spend on it ( need at least 5 days if want to get past the withdrawal symptoms ) then might cut out gluten for a while. But just recently got so fed up of yoyoing from wheat to non-wheat [ because although I'm calmer, more stable, more in the world, less alienated, more able to relate to people , less black-and-white logic-driven,more able to handle noises and smells and inconsistencies ( ! !! ! ) I miss my wheaty ASD'ish self too much , as if am tranquilised , when excluding gluten] that i've decided to experiment with eating just TINY TINY amounts of wheat/rye etc each day so that maybe can keep the seductive buzz of analysing and extrapolating and creating meanings and so on etc, while hopefully not experiencing too many of the negative effects.
Another one is definitely sport , but the trouble is that when I'm depressed I don't want to do it.
And sunshine, which is why I hitched to the South of France 9 years ago , deliberately for the sun.