I remind myself that its better than the time I had my very own Personal Great Depression, which lasted for 14 months straight. No good days, no rays of sunshine, just utter darkness that seemed to go on forever....
"Atleast it will be over soon"
"This too shall pass"
"The tide will change"
These are my silverlining mantras...
No it doesn't fix it, but clinging to a healthy perspective is the point for me.
Its exhausting, its discouraging, its mentally, physically and emotionally draining, but atleast I get a breather soon, unlike the folks who stay on one end of the pendulum for months on end.
I don't actually have advice on how to combat them or slow them down, (idk if that's even possible tbh) but I do recommend working healthy hedonism into your schedule as it atleast helps to counter the effects of rapid cycling.
Whether its an hour a day, or 1 day per week, use the time to decompress, regroup, and do something to sooth your soul. Something that's just for you, could be a favourite treat, going to relax at your favourite spot, a scenic drive, a bubble bath that ONLY ends when YOU decide, or even just using the time for doing absolutely nothing and commit to simply being, if you're one of the humandoing types... ( I used to be a humandoing

but I have devolved back to my natural state and am now succesfully a humanbeing again)

...
Incorporating this into my lifestyle has helped much in being able to bounce back from the toll BP takes on my mind and body.