You're being too hard on yourself, you are just learning to cope and are still suffering from the symptoms that anxiety causes. You see all these crappy feelings are caused by the anxiety. The crappy feelings are the AFTER EFFECTS of anxiety and BEFORE you took your Son for the flu shot you were worked up, you were ANXIOUS.
So although you dealt very well with taking your son for his flu shot (because you DID NOT CONCENTRATE ON YOUR SYMPTOMS and distracted your mind instead), AFTERWARDS you made the mistake of going back to concentrating on your symptoms and it is the concentrating on your symptoms again that is causing you further anxiety - and that leads on to becoming convinced that there is no hope because all you can see are these damn symptoms again - and that just brings further anxiety.
What you need to realise is that it is anxiety that causes the symptoms and the symptoms that causes anxiety and to break that we have to not get anxious. So you because you did get anxious BEFORE the "event" (and the "event" can be absolutely anything) you had the shakes, sweats, dizziness, etc. and were afraid of what MIGHT happen - you are paying the price.
The "price" is that you filled your body with all the chemicals (and all the chemical reactions) that are released when we pump ourselves full of adrenalin, which is what you had done by getting all worked up. Now when you do that then AFTERWARDS their is a "crash", their is a period where we experience SYMPTOMS and those symptoms innumerable and are simply the after effects, the "coming down", caused by all the chemicals that are released into our systems when we are anxious. And this is a perfectly natural phenomena that we simply misunderstand.
Your current trouble then is that you are getting anxious before the event and then experiencing all the symptoms of that anxiety afterwards. The "secret" then is to realise that you DO NOT NEED to get worked up BEFORE the event because there IS NOTHING to worry about DURING the event (and you have proved that for yourself), but if you do get worked up at any point then, as sure as night follows day, the symptoms will follow the anxiety. If they do then you just have to accept they are there, because you got anxious in the first place - fighting the symptoms is the madness, because the symptoms are an inevitable effect of anxiety.
So, IF you can stop getting worked up before the event then there will be no coming down, no symptoms, after the event and IF there are no symptoms after the event then there will be nothing for you to add further worry to and further perpetuate your anxiety with.
When you don't get anxious any more OR when you don't get anxious because you are experiencing symptoms that have arisen (IE: are an after effect) from an anxiety inducing "event" - then you can probably say you are cured of anxiety - until then you will "suffer" from anxiety.