You Forget 90% of your DreamsWithin 5 minutes of waking, half of your dream if forgotten. Within 10, 90% is gone. The famous poet, Samuel Taylor Coleridge, woke one morning having had a fantastic dream (likely opium induced) - he put pen to paper and began to describe his vision in a dream in what has become one of English most famous poems: Kubla Khan. Part way through (54 lines in fact) he was interrupted by a Person from Porlock. Coleridge returned to his poem but could not remember the rest of his dream. The poem was never completed.
In Xanadu did Kubla Khan
A stately pleasure-dome decree:
Where Alph, the sacred river, ran
Through caverns measureless to man
Down to a sunless sea.
Curiously, Robert Louis Stevenson came up with the story of Doctor Jeckyll and Mr. Hyde whilst he was dreaming.