心甘情愿 He did all this of his own accord.
心不在焉 You look absent-minded; what's wrong?
心满意足 The little boy sat there smiling, as happy as a clam.
心力交瘁 I don't know what to do. I just burned the candle at both ends.
心灰意冷 He was in black despair when he failed in the joint examination.(down in the bushes/in the dumps/lose heart)
心有余悸 A burned child dreads the fires. (Once bitten, twice shy.)
心安理得 No matter what he said, I have the peace of mind. (have an easy conscience)
心血来潮 He did it just on the impulse of the moment.
心花怒放 My heart sings with joy because I receive over 300 letters a week from people around the world.
小Car笔记：
dread：惧怕，恐惧 【常用词组】① in dread of someone：害怕某人 ② in dread of one's life：害怕有生命危险
impulse：冲动，心血来潮 【常用词组】① impulse buying：即兴购买，未经考虑仅凭一时冲动的购物行为 ② electrical impulse：电脉冲