If counting sheep is an abstract concept, or you are unable to visualise the faces of loved ones, you could have aphantasia -- a newly defined condition to describe people who are born without a "mind's eye."
Some people report a significant impact on their lives from being unable to visualise memories of their partners, or departed relatives. Others say that descriptive writing is meaningless to them, and careers such as architecture or design are closed to them, as they would not be able to visualise an end product.
See further in this article from Science Daily
and in this one from Business Insider: One in 50 people have a rare disorder that prevents them from picturing a beach in their head