“but it's no use going back to yesterday, 

because i was a different person then”

“be what you would seem to be
- or, if you'd like it put more simply - 
never imagine yourself not to be otherwise than what it might appear to others 
that what you were or might have been was not otherwise than what you had been 
would have appeared to them to be otherwise.” 

Carroll, L. (1832-1898), in Alice in Wonderland