Hi angela :) Well, out of the blue P/A's are the worst I reckon..and yes that choking feeling is terrifying..but you know what? You survived! And that's great because it means that you can take control..you did the right thing by slowing your breathing - well done! Did you have a stressful day, is there some underlying stress happening with you, if so is there some way you can work towards fixing these probs?
Take good care.