I think I can guess what you're referring to, and I have had (and have) similar issues... I have pretty much squandered my opportunities though, so I might not be the best person to talk to about this.

Anxiety is treatable. I know you're seeing a psychologist - is that helpful for you at all? I assume you're on Christmas break from therapy right now, too? Things always get worse over the holidays. (Did you have a good Christmas/NY holiday? I hope you did.)

For me, the feelings of anxiety are tied to loneliness - that's something it has taken me over two years of therapy to realise fully. I'm not sure if it's the same for you, though. I think the underlying reasons are probably different for everybody. But being an academic is a lonely life (although in your field it's more common to work in teams than it is in my field - still, there's always the expectations to do as well as the other people in the group.) You're still training for this job. And it's a lifelong training process.

Not sure if any of this is helpful at all. The short answer is, I think, to try to work out what is at the bottom of the anxiety.

Also, remember that all you need to do is take one step at a time. Focusing too much on the distant goal is never a good idea, at least not for me. It's how I almost didn't finish my PhD - I kept thinking about the finished book instead of focusing on finishing a chapter, or a section of a chapter, at a time... but again, this is individual.