Watson: "A Christian is like a ship at anchor...."

In Thomas Watson's discussion of the "Thy kingdom come" petition in The Lord's Prayer, he lists thirteen things from which believers shall be freed from when Christ's kingdom fully comes.  In the eighth point ("In the kingdom of heaven we shall be freed from all doubts and scruples"), Watson includes this picturesque line:  "A Christian is like a ship at anchor, which, though safe, may sometimes be tossed upon the water."

Here's the eighth point in entirity:

In the kingdom of heaven we shall be freed from all doubts and scruples. In this life the best saint has his doubting, as the brightest star has his twinkling. If there were no doubting, there would be no unbelief. Assurance itself does not exclude all doubting. ‘Thy loving kindness is before mine eyes.’ Psa 26: 3. At another time, ‘Lord, where are thy former loving kindnesses?’ Psa 89: 49. A Christian is like a ship at anchor, which, though safe, may sometimes be tossed upon the water. Sometimes a Christian questions his interest in Christ, and his title to the promise. As these doubting eclipse a Christian’s comfort, so they bear false witness against the Spirit. But, when the saints shall come into the kingdom of heaven, there shall be no more doubting; the Christian shall then say, as Peter, ‘Now I know of a surety that the Lord has sent his angel and has delivered me.’ Acts 12: 11. Now I know that I am passed from death to life, and I am got beyond all rocks, I have shot the gulf, now I am in my Saviour’s embraces for ever.

JTR