Ever since grandmother died, grandfather has been eating his heart out--he’s lost all interest in life and won’t even get out of bed to eat.

这个人说："自从祖母去世后，祖父非常伤心，他对生活失去了一切兴趣，都不愿意起床吃饭。"To eat one’sheartout还可以用在另一种场合，也就是半开玩笑地让别人对你产生妒忌。你听了下面这个例子就会明白它的意思了。这是一个大学生在对他的要好朋友说话