I worry about running out of money. It hasn't happened yet but times are getting harder for most ordinary people and I don't know that process is going to stop before I can't make ends meet any more.
Also about money, I worry that one of these days I won't be able to transfer sterling to dollars any more. The online currency exchange process has always worked before (in the end), but they keep changing the websites and the hoops I have to jump through to get it to work, and I fear that one of these days it'll go wrong in a way I can't fix. I'm usually a bag of nerves every time I try to do a currency exchange. There are expensive alternatives to the way I usually do the job, but they're - well, expensive - and that would feed into my aforementioned fear about running out of money.
I worry about service providers changing in such a way as to make it impossible for me to access the services I need in order to survive. They seem to make it more difficult for me all the time, and one of these days I fear they'll go and do something that makes it impossible.
I worry about something going wrong with my UK house that I can't afford to fix.
I worry about something going wrong that gets me stranded when I try to travel alone between the UK and the USA.
I worry about one of my computers going so badly wrong that I can't rescue important files and can't access online services any more. I've got most stuff backed up and I've got more than one computer, but it's hard to keep the backups fully updated, especially as I need at least 2 backups on separate devices to even be reasonably sure that I won't lose anything important.
I worry about my loved ones when they unexpectedly can't be contacted, especially when it's hard to think of an explanation that doesn't involve something very bad happening to them.
I worry about my health when I get any symptoms that could indicate something is seriously wrong. I worry about growing old and being no longer able to look after myself. I worry about dying of old age, and about becoming physically unable to get around.
I worry about losing my singing voice or my other musical skills. It's very useful for getting accepted by people, and without it I'd be quite lost socially. But musicians usually do get too old to perform very well, eventually.
Still, none of it usually keeps me awake at night. My worries are just a nagging thing that takes the edge off my happiness.