心, literally heart, is mostly used with the meaning of mind, feeling, mood, emotion etc. because the heart was seen as the thinking organ in the ancient time.
用心
1.attentive(ly) or diligent(ly)
2.an intention or motive; care
3.at pains
我们的服务生真的很用心，不是吗？Wǒ men de fú wù shēng zhēn de hěn yòng xīn, bù shì ma? Our server is really attentive, isn’t he?
我是歌手，我要用心地唱喜欢的歌！Wǒ shì gēshǒu, wǒ yào yòng xīn dì chàng xǐ huān de gē! I am a singer, and I want to diligently sing the songs that I like!
妻子明白了曾子的用心，羞愧地说：“有道理。”qī zi míng bái le zēng zǐ de yòng xīn , xiū kuì de shuō : ” yǒu dào lǐ 。” “Zengzi understand the intentions of his wife, shame said: ” The truth.
More collocations of 心: 小心, 劳心, 狠心, 伤心, 醉心, 甜心, 痴心.