Anything can cause it. When anything suddenly happens that's out of my control. I have to remind myself to stay grounded and present when it hits.

Being in unfamilier places is worse but normally it just comes on and though I don't know what dying feels like I feel like everything is sureal and im about to die. over the years ive got somewhat used to it and tailerd my life around it. it doesnt happen so often but when the black dog visits its very dark and scary.

Anything can trigger anxiety, so I take herbs, early morning walks, eat fish, and take a certain calming plant.

Are you talking about anxiety or panic attacks?
I have suffered from panic attacks for a long time and have thought about it a lot.
I have come to the conclusion that anxiety and panic attacks are a type of OCD, Obsessive Compuslive Disorder. It is brought about by mental triggering in selective situations in each individual. Rather like Sheldon Cooper, who must ritualisticly knok on every door three times.
An indiviual relieves stressful situations in life by adopting patterns of thinking and behaving. These patterns become habits and crutches until they are rituals which the indiviual must obey to relieve the stress. Origionaly, it took a lot of stress to bring about the compulive thinking but over time it only takes a little stress to bring it about.
I am not a doctor or phycologist, this is only my opinion based upon my own experience.

I procrastinate a lot, especially regarding things I don't want to do to begin with, and panic when I realize I waited too long to do something I need to do. I generally don't sleep well when there's a lot to do because I put things off.

It wasn't much of an issue before trump and the recent wave pro mega rich legislation but I would have been looking at retiring in about 10 years and now I fear I will have to work til death. That in turn makes me wonder how I will remain employable beyond a certain age.