1. 习以为常了。

[ xí yǐ wèi cháng le 。 ]

That's always the case.

2. 他自以为是重要人物，但我们觉得他什么也不是。

[ tā zì yǐ wèi shì zhòng yào rén wù ， dàn wǒ mén jué dé tā shén me yě bù shì 。 ]

He thinks himself somebody, but we think him nobody.

3. 我以为他很聪明，其实他是个蠢货。

[ wǒ yǐ wèi tā hěn cōng míng ， qí shí tā shì gè chǔn huò 。 ]

I supposed him to be very clever but he was in fact a fool.