Become discouraged, as in The rescuers worked hard for the first few hours, but then they lost heart. This term uses heart in the sense of “courage” or “spirit.” [Mid-1800s] Also see lose one's heart to.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use lose heart in a sentence
Not for a moment did the brave man lose heart or suffer himself to grow weary in his difficult task.A short history of Rhode Island | George Washington Greene
I felt that if I thought the matter over I might lose heart, so I suddenly bounded into the arena.The Adventures of Louis de Rougemont | Louis de Rougemont
But don't you lose heart, Jim, for I'm sure this isn't the end of our story, by any means.Dorothy and the Wizard in Oz | L. Frank Baum
A young soldier must not lose heart because he finds he is a prisoner.The Young Castellan | George Manville Fenn
But weeds have this virtue: they are not easily discouraged; they never lose heart entirely; they die game.A Year in the Fields | John Burroughs