Anxiety
Freud maintains that every dream, no matter how nightmarish or distressing, is the expression of an un-fulfilled wish. But surely, one might argue, our nightmares are often of our worst fears--of thing we would never wish to happen. Freud explains these nightmares as anxiety dreams. These dreams are still wish-fulfillments. However, our unconscious desires are often things we find ourselves unable to tolerate or acknowledge. For example, taboo sexual desires, or rage or jealousy against one's friends or family. A person experiences anxiety over these wishes, because his conscious self is fighting against forbidden desires. These wishes then manifest in dreams.Keeping in mind our assumptions in regard to the two psychic instances, we may now proceed to say: disagreeable dreams, as a matter of fact, contain something which is disagreeable to the second instance, but which at the same time fulfils a wish of the fist instance. -The Interpretation of Dreams, p.122
In an anxiety dream, the unconscious (or repressed) desire manifests itself, while at the same time the conflicting desires fight against them.