What does your conscience say? You should become who you are.
 
[Was sagt dein Gewissen? — „Du sollst der werden, der du bist.”]

Friedrich Nietzsche (1844-1900) German philosopher and poet

The Gay Science [Die fröhliche Wissenschaft], Book 3, § 270 (1882) [tr. Nauckhoff (2001)]
    (Source)

Also known as La Gaya Scienza, The Joyful Wisdom, or The Joyous Science.

(Source (German)). Alternate translations:

What Saith thy Conscience? -- "Thou shalt become what thou art."
[tr. Common (1911)]

What does your conscience say? -- "You shall become the person you are."
[tr. Kaufmann (1974)]

What does your conscience say? "You shall become who you are."
[tr. Hill (2018)]