3 sentences

1. 很难保持温度恒定。

   hěn nán bǎo​chí wēn​dù héng​dìng.

   It is difficult to maintain a constant temperature.

   Source: CCMatrix

2. 我发现自己很难保持清醒。

   wǒ fā​xiàn zì​jǐ hěn nán bǎo​chí qīng​xǐng.

   I found it hard to stay awake.

   Source: CCMatrix

3. 当你触碰别人时，很难保持生气。

   dāng nǐ chù​pèng bié​ren shí, hěn nán bǎo​chí shēng qì.

   It’s hard to stay angry when you touch someone.

   Source: CCMatrix