我知道你神经
[wŏ zhī dào nĭ shén jīng]
This reads as 'I know you are nervous / on edge'. But more contextually among friends in informal language, '神精' (a phonetic resemblance to 'shenjing' which can mean nerves) can also mean quirky or unique, so it may suggest knowing or understanding the peculiarities or quirkiness of someone.