What Lexie said times three. Unless you have a really concrete reason, keep your scores.

The way the computer test works, you may very well think you did terribly, when in fact you did fine. That's because the computer test will set the difficulty of each question based on how well you did on the questions before it. So it's very possible most of the questions will seem on the hard side, and you shouldn't be surprised by that.

It's kinda evil, really. But if you know the deal beforehand, I think it's much easier to cope with.