根據Free Dictionary的解釋，eat one's heart out是指羨慕吧，憂傷的心，嫉妒吧~

?They just make you eat your heart out.

?他們真讓你傷心透了。

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

? 羨慕吧！我們已經贏得了總冠軍的稱號。

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

? 你們就眼紅我吧，薩姆中彩票后對朋友們說道。

heart在口語中也很常見，來學習一些其他的表達：

1 wear your heart on your sleeve流露感情

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

?最好不要輕易地流露感情。

2 heart and soul全心全意的

?They threw themselves heart and soul into the project.

? 他們全心全意地投入了這個項目。

3 heart leaps怦然心動；內心雀躍

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

?什么樣的禮物能讓她怦然心動？

4 my heart bleeds for sb為...感到難過；為...感到傷心

?My heart bleeds for the poor child.

?我為這個可憐的孩子感到心痛。

（來源：滬江英語）