自考英语专业综合英语第一册上第9课deep down理解

在第9课第198页上有一句，
but deep down they are miserable
用英语解释：
but the pain in their hearts was terrible,
deep down含义就是，内心深处，例如，
She seem s indifferent, but deep down she's very pleased.
她貌似无动于衷，其实心里非常高兴。
He seems confident but deep down he's quite insecure.
他好像很有信心，实际上却没什么把握。