Reduce one's goals or aspirations, as in Once he got the job I'd applied for, I had to lower my sights. This expression alludes to taking aim through the sights of a firearm. Also see raise one's sights; set one's sights on. [Second half of 1900s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.