breathe easy - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Also, breathe easily or freely. Relax, feel relieved from anxiety, stress, or tension. For example, Now that exams are over with, I can breathe easy, or Whenever I'm back in the mountains, I can breathe freely again. This idiom originally (late 1500s) was put as breathe again, implying that one had stopped breathing (or held one's breath) while feeling anxious or nervous. Shakespeare had it in King John (4:2): “Now I breathe again aloft the flood.” The variant dates from the first half of the 1800s.