Don't single yourself out! Know that you aren't the only one who has to struggle with a retake. I, too had to deal with retaking when I somehow scored a 7 in Verbal when I was averaging 10-12 in practice. It was a blow to my confidence and also an "Oh @%$#" moment when I realized I had to go through the ordeal again.
For me, it was the constant reminder that I must work hard, no matter what. If not now, then I will at some future point in life. It's OK to mope and commiserate once in a while, but in the end that gets you nowhere, and you can be sure that a future employer won't expect you to cry a failure off, but to learn from it, shrug it off and move on.
Finally, don't take for granted that you have the ability to score in your desired range in practice - many people would probably kill for that kind of reassurance and potential. If you can do it multiple times, you can certainly pull it off on the real thing, and that much is certain. We all choke - sometimes it doesn't happen at the best of times but we make do. Chin up, and practice, practice, practice!
Good luck on your retake!