Also, every moment counts. Time is of the essence. For example, Hurry up with those tools—every minute counts, or In performing surgery every moment counts. This idiom uses count in the sense of “to enter into the reckoning” (and hence be important).
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.