The maxims tell you to aim at perfection, which is well; but it's unattainable, all the same. [ Bayard Taylor ]

Unattainable wishes are often called pious. This seems to indicate that only profane wishes are fulfilled. [ Marie Ebner-Eschenbach ]

Aim at perfection in everything, though in most things it is unattainable; however, they who aim at it, and persevere, will come much nearer to it than those whose laziness and despondency make them give it up as unattainable. [ Chesterfield ]

Bright and illustrious illusions! Who can blame, who laugh at the boy, who not admire and commend him, for that desire of a fame outlasting the Pyramids by which he insensibly learns to live in a life beyond the present, and nourish dreams of a good unattainable by the senses? [ Bulwer-Lytton ]