Can your nightmares be a glimpse of the future?

Some nightmares could be a glimpse of the future because there is such thing as a dream come true but this happens rarely, nightmares are mostly not a glimpse of the future but it is normally what we want to believe.

Nightmares and other dreams can glimpse the future in the same way that a weather report will forecast future weather conditions. In real life, the conscious mind naturally filters information perceived through the senses. Much of this is the mind's normal limitation, but some is due to denial and wishful thinking. But the subconscious mind can pick up much more information and recognize trends and patterns that are missed by the conscious mind. This information can lead to obvious conclusions which sometimes appear in dreams or nightmares as visions of the future. Such dreams can be alarmingly accurate, but there is nothing supernatural or magic involved.
Not necessarily, if you see your dreams begin to start coming true you could be a psychic.

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In the vast majority of cases, the answer is no, dreams do not predict the future. Dreams arise from the subconscious mind and although they sometimes seem to present amazing information, the fact is that they draw from our own memories, emotions and intuition, not from any supernatural sources. Many times what seem to be prophetic dreams are nothing more than subtle impressions that the subconscious mind combines with intuition. These dreams might "forecast" the future in exactly the same way the weather report will "forecast" next week's storm, by following the evidence to its obvious conclusion.