OP, a lot of people don't understand anxiety. I have been ripped to shreds on MN when I have posted a couple of anxiety issues, with people telling me to "get a grip" and that they feel sorry for my DC. Some people can be downright nasty about it.
I can't help suffering from anxiety and I always have. I hate being late, I hate not being organised, I hate plans changing at the last minute because I have psyched myself up for what I thought was happening. It is horrible to not be in control of your own feelings/emotions.
As another PP said, people are now being encouraged to talk about their mental health issues. More people are seeking counselling, which then gives a name to their problem (as happened to me, I didn't realised that what I had suffered from for years was anxiety).
If something goes wrong then I think about it over and over, I can't just switch off or let it go, I have to replay it over and over.
I am on mild beta blockers for my anxiety and I do feel much better now a lot of the time. I also challenge myself to do something, and then the second time you do it, you can think to yourself, this is easy I have done it before.
But simple things that others take for granted, or even look forward to, like travelling to new places, holidays, concerts etc, can cause a huge amount of anxiety for me, and people who don't suffer from it, just don't understand it :(
I also see the worst case scenario in everything.
So if your employee makes a little mistake, or has a meeting to face, or new clients, these things could be making them anxious. Or maybe deadlines are too tight, or the workload is too heavy. It would also be different for each individual.