Hey Bill
You nailed it, depersonalization (DP) and derealization (DR) are 2 really scarey side effects of anxiety and panic.
They are uncomfortable, you hate that feeling, it is scarey [b]but[/b]it is normal and will pass with time.
It is the direct result of fatigue. Stress, constant worry, [b]what if[/b] thinking all exhaust the body and the mind. Your mind can only take so many days and it will start to detatch (DP/DR) so it can recharge. It you think of it as a battery that is low and needs to be plugged into something so it can be recharged it doesnt seem so scarey.
It is common when you are experiencing this to also add to the symptoms by breathing shallow, cause you are frightened. Feeling lightheaded, feeling a fullness in the head, numbness, all tension and stress.
Best thing to do is accept the feelings, keep telling yourself that you are tired, stressed out. Next best thing is to do something that takes your mind off of yourself. Go play a game on the computer, chill out, take a nap. Be good to yourself.
You might enjoy reading "Hope and Help For Your Nerves" by Claire Weekes. It was written @ 1969, but it still applies (the best I have ever read) to today.