be frank and forthright(/unreserved); be truthful in one’s words; carry(/wean) one’s heart upon one’s sleeve; say what one thinks; speak from the (/one’s)heart; speak the mind
? 就是我們……和幾乎同類的人，只要什么地方有些不同，又得～，就往往免不了彼此無話可說。(《魯迅選集》 Ⅳ—36) Even we…of ten find nothing to say to people who are more or less our own counterparts if we fail to see eye to eye yet have to speak from the heart.
心口如一xīn kǒu rú yī
心里想的和嘴上說的都一樣。形容為人誠(chéng)實(shí)、直爽。be honest and straight forward, say what one thinks, speak the minds, mean what one says, be frank and forthright