Anxiety receeds then comes back with a vengence

So I'm no stranger to anxiety attacks. In fact, been having them over 20 years. I found recently that I hadn't had one for a few months, I was dealing pretty well. Then all the sudden when I went to a familar public place that I usually am very comfy in, I found my hands shaking, I was confused, my chest was tightning...

I was then triggered again by a flashback a week later, first time that's happened, and I cried with the same symptoms as I said above. What the heck? I thought I got over this? Is it common for them to go away and then come back more frequently and worse than before???