Adams on Psalm 71:18

18 Forsake me not; until, etc Apostasy in old age is fearful. He that climbs almost to the top of a tower, then slipping back, hath the greater fall. The patient almost recovered, is more deadly sick by a relapse. There were stars struck from heaven by the dragon's tail (Re 12:4); they had better never have perched so high. The place where the Israelites fell into that great folly with the daughters of Moab, was in the plain, within the prospect of the Holy Land; they saw their inheritance and yet fell short of it. So wretched is it for old men to fall near to their very entry of heaven, as old Eli in his indulgence (1 Samuel 2); old Judah in his incest (Genesis 38); old David with Bathsheba; old Asa trusting in the physicians more than in God (2 Chr 16:12); and old Solomon built the high places. Some have walked like cherubs in the midst of the stones of fire, yet have been cast as profane out of God's mountain. Eze 28:14, 16. Thus the seaman passeth all the main, and suffers wreck in the haven. The corn often promises a plenteous harvest in the blade, and shrinks in the ear. You have seen trees loaden with blossoms, yet, in the season of expectation, no fruit. A comedy that holds well many scenes, and goes lamely off in the last act, finds no applause. Remember Lot's wife (Lu 17:32): think on that pillar of salt, that it may season thee.

As quoted in Spurgeon's Treasury of David.