wear one's heart on one's sleeve（把情感表露出来）

意思是"to make one's intimate feelings or personal affairs known to all（张扬，外露，坦率）"，尤指感情上的外露；其实也就是"expressing your emotions freely and openly ...（大胆的说出你的真实感受）"。

请看例句：

She's a shy person. She's never been one to wear her heart on her sleeve.

她是个害羞的人，从来不敢把心里的真实想法表达出来。

Alan: This is life and death. Your wife is lying in a coma. You, you don't even make a pretense of caring, do you?
Alan：这是生死大事，你的妻子正处于生死状态，你连假装关心下都不行吗？
Claus: Of course I care, Alan. It's just, I don't wear my heart on my sleeve.
Claus：当然，我当然关心啦，只是我不擅于言表而已！

BTW: 这段对话是出自《Reversal of Fortune（命运的逆转）》