根据Free Dictionary的解释，eat one's heart out是指羡慕吧，忧伤的心，嫉妒吧~

▷They just make you eat your heart out.

▷他们真让你伤心透了。

▷Eat your heart out! We won the championship title!

▷ 羡慕吧！我们已经赢得了总冠军的称号。

▷ "Eat your heart out", Sam told his friends after winning the lottery.

▷ 你们就眼红我吧，萨姆中彩票后对朋友们说道。

heart在口语中也很常见，来学习一些其他的表达：

1 wear your heart on your sleeve流露感情

▷It is better to not wear your heart on your sleeve.

▷最好不要轻易地流露感情。

2 heart and soul全心全意的

▷They threw themselves heart and soul into the project.

▷ 他们全心全意地投入了这个项目。

3 heart leaps怦然心动；内心雀跃

▷What kind of gift can make her heart leaps up?

▷什么样的礼物能让她怦然心动？

4 my heart bleeds for sb为...感到难过；为...感到伤心

▷My heart bleeds for the poor child.

▷我为这个可怜的孩子感到心痛。

（来源：沪江英语）