3 sentences

1. 你一整天都心不在焉。

   nǐ yī​zhěng​tiān dōu xīn​bù​zài​yān.

   You've been absentminded all day.

   Source: OpenSubtitles

2. 你有点心不在焉。

   nǐ yǒu​diǎn xīn​bù​zài​yān.

   You seem a bit distracted.

   Source: OpenSubtitles

3. 当你注意到自己心不在焉时，微笑，然后轻轻地回到呼吸上。

   dāng nǐ zhù​yì dào zì​jǐ xīn​bù​zài​yān shí, wēi​xiào, rán​hòu qīng​qīng de huí dào hū​xī shang.

   When you notice your mind wandering, smile, and simply gently return to your breath.

   Source: CCMatrix