Peras imposuit Iuppiter nobis duas:
propriis repletam vitiis post tergum dedit,
alienis ante pectus suspendit gravem.
hac re videre nostra mala non possumus;
alii simul delinquunt, censores sumus.
(Phaedrus, Fab. 4.10)
Jupiter has given us two sacks to carry. He put one sack, filled with our own faults, on our back, and he suspended a sack heavy with the faults of others in front of us. This is the reason why we are blind to our own bad habits but we sit in judgment as soon as others make a mistake. (tr. Laura Gibbs)