The Christian is like a man making his way up a hill, who occasionally slips back, yet always has his face set toward the summit. The unregenerate man has his face turned downwards, and he is slipping all the way. —A. H. Strong

The believer, like a man on shipboard, may fall again and again on the deck, but he will never fall overboard. — C. H. Spurgeon

Both quotations are cited in Loraine Boettner’s, Reformed Doctrine of Predestination, pp. 188-189.