In my LDs I tend to purposefully summon things that I know I would be afraid of, and it helps me feel more in control. Dolphin was right on the money with his answer. Just confront whatever nightmarish element that's bothering you and you'll probably find that it's not all that bad. And by confront, I don't mean fight/attack. The one time I did that it didn't end well!

Basically, if you're not responding with fear or anger towards whatever it is that's antagonizing you, you'll be all right.

Good luck if it happens again!