From Longman Dictionary of Contemporary Englishnot have the heart to do somethingnot have the heart to do somethingCAN'Tto be unable to do something because it will make someone unhappy I didn’t have the heart to tell her that her beautiful vase was broken. → heart
Examples from the Corpus
not have the heart to do something• I didn't have the heart to tell my daughter we couldn't keep the puppy. 