Those are the scariest kind of attacks. The ones that come out of nowhere....because you are so calm beforehand you can't believe it is only anxiety and you think it's something really worse. I was gardening one day...relaxed, just like you said, and it happened to me. And I thought this cant be a panic attack....I was feeling fine, it must be a stroke or heart attack, and then it really escalates. That attack lasted most of the day. You really should use your meds when you need them. I never take mine every day, only when I feel anxious, but I am on Lexapro now, and it seems to be helping.