not have the heart
To not have the emotional resolve (to do something); to be unable to do something, especially that which is or seems callous or unsympathetic. I didn't have the heart to tell her that I didn't love her anymore. How could you fire someone the day after their father died? I wouldn't have the heart.
not have the heart to do something
Fig. to be too compassionate to do something. I just don't have the heart to tell him the bad news.
not have the heart to
Be unable to bring oneself to say or do something, as in He didn't have the heart to tell her the cat had died. [Mid-1600s] Also see have a heart.
not have the ˈheart (to do something)
not be able or willing to do something which could hurt somebody else: I didn’t have the heart to take the money from him — it was all he had.