That sounds like familiar territory!
My personal best bet is to begin by noticing that I've just used the words "everything" and "can't". Twice each, in fact. And then I remind myself that there's a high probability that what I just said/thought isn't literally true, even if it feels like it is.
Step 2 would maybe to to remember to breathe, because I'm probably not doing that real well.
Step 3 would be to look for some small bit of the rat's nest of problems that seems potentially solvable (one end of the string) and see if I can do something about that, while (hopefully) ignoring the rest. Then one step at a time, until you have a long, straight string, instead of a rat's nest. (I also make an effort NOT to ask myself "What else can go wrong?" because it seems like when I do that I usually find the answer. :nailbiting:)
Sending you good and hopeful thoughts!