3 sentences

1. 别灰心，你要振作起来。

   bié huī​xīn, nǐ yào zhèn​zuò qi​lai.

   Don't lose heart; you need to cheer up.

   Source: Dong Chinese Dictionary

2. 别灰心，你还有我们这些朋友。

   bié huī​xīn, nǐ hái​yǒu wǒ​men zhè​xiē péng​you.

   Don't lose heart; you still have us as your friends.

   Source: Dong Chinese Dictionary

3. 虽然这次考试没及格，但你千万不要灰心。

   suī​rán zhè cì kǎo​shì méi jí​gé, dàn nǐ qiān​wàn bù yào huī​xīn.

   Even though you failed the exam this time, you must not lose heart.

   Source: Dong Chinese Dictionary