nerve

• 亏你还好意思说呢！

  Imagine you having the nerve to say that!

• 不好意思

  excuse me

• 总是落在人家后面，真不好意思

  so sorry for always falling behind

• 向人请教有什么不好意思。

  There's nothing to be ashamed of in asking for help.

• 他很忙，不好意思打搅他。

  He's very busy, so I would feel bad disturbing him.