Thanks for the responses and thoughts everyone. Sunny, like everyone else said, the ripple analogy is just perfect.
I do have a lot of acquaintances....people that I will stop to say hi to and chat with, etc. But it's exactly one or two of those closer friends that I miss - people you can talk to about more serious things, and build a longer lasting relationship with.
It is interesting who ends up staying your friend. I've had this same experience with graduating from high school and college. You sort of expect that you'll stay in touch with different people, but in reality sometimes your longer lasting friends aren't the ones you expect at all. I do have some closer friends from my high school years, but we all live in different places and don't get to see each other face to face all that often. We exchange e-mails sometimes, which is nice, but it's not quite the same as being with someone.
I am very lucky to have a boyfriend who is also my best friend, and I don't want to count him out as one of those inner circle friends. But you need someone to talk to outside of that sort of relationship, too, I think.
Thanks Stewed for sharing that you went through a similar time after leaving your job. They were definitely the sorts of friends that were about hanging out and socializing but not that deeper friendship. Some of them maybe don't know what to say because they don't understand the anxiety, but I think real friends say something, even if they don't understand what you're going through with anxiety. I've been able to tell who my real friends are when they try to understand what I'm going through, or at least acknowledge that it must be tough and that they are supportive of me, even if they don't really get what a panic attack is. It's the ones that stop saying anything at all that are most painful.