Spurgeon, "Christ's People- Imitators of Him"

The fact that perfection is beyond our reach,
should not diminish the fervor of our desire after it.

The Christian man; though he feels he never can mount to the
heights of complete excellence, and perceives that he never can
on earth become the exact image of Christ, still holds it up
before him, and measures his own deficiencies by the distance
between himself and Jesus.

This will he do; forgetting all he has attained, he will press
forward, crying, 'Excelsior!' going upwards still, desiring to be
conformed more and more to the image of Christ Jesus!