I had set foot in that part of life beyond which one cannot go with any hope of returning.

[Io tenni li piedi in quella parte de la vita di là da la quale non si puote ire più per intendimento di ritornare.]

Dante Alighieri (1265-1321) Italian poet

La Vita Nuova [Vita Nova; New Life], ch. 14 (c. 1294, pub. 1576) [tr. Reynolds (1969)]
    (Source)

Said to his friend after seeing Beatrice at a wedding feast (perhaps her own to Simone de’ Bardi), at which point his passion for her has have been set.

(Source (Italian)). Alternate translations:

Of a surety I have now set my feet on that point of life, beyond the which he must not pass who would return.
[tr. Rossetti (c. 1847; 1899 ed.)]

I have set my foot in that part of life, to pass beyond which with purpose to return is impossible.
[tr. Martin (1862)]

I have held my feet on that part of life beyond which no man can go with intent to return.
[tr. Norton (1867)]

I have placed my feet on those boundaries of life beyond which no one can go further and hope to return.
[tr. Musa (1971)]

I have just set foot on that boundary of life beyond which no one can go, hoping to return.
[tr. Hollander (1997)]

I have set foot in that region of life where it is not possible to go with any more intention of returning.
[tr. Kline (2002)]

My feet were at the edge of life beyond which one cannot pass with an expectation of returning.
[tr. Appelbaum (2006)]

I have set my feet in that place in life beyond which one cannot go with the intention of returning.
[tr. Frisardi (2012), ch. 7]