H. P. Lovecraft 
The Silver Key 

A man discovers, at the age of 30, that his daily waking exposure to the more practical, scientific ideas of man, has eventually eroded his ability to dream as he once did, and has made him regretfully subscribe more and more to the mundane beliefs of everyday, waking real life. Not certain which is truer, he sets out to determine whether the waking ideas of man are superior to his dreams.