You Forget 90% of your Dreams

Within 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’s 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.

Curiously, Robert Louis Stevenson came up with the story of Doctor Jeckyll and Mr. Hyde whilst he was dreaming. Mary Shelley’s Frankenstein was also the brainchild of a dream.
- Source: The List Universe