How to guard from carnal thoughts and actions. What will do it?

I am reading and studying the John Bunyan book Pilgrim's Progress. John Bunyan wrote this book in 1678. I am using a study guide from Mount Zion Bible Institute (free) and also notes and commentary from Ken Puls of Founder's Ministries/Founder's Press.

I absolutely love the language of the old Puritan times. At one point, Christian had fallen asleep and now had to retrace his steps because he had lost his scroll. The sun was setting and he worried would not make it to the safe and secure way-station Porter's Lodge before dark. He had been told there were lions awaiting (though chained). He was nervous about the noise the doleful creatures would make.

I wrote this during my reflection time-

When I stray from the righteous path or lose my scroll, the night time noise of the doleful creatures disturbs my heart and troubles my mind.

Christian made it to the Porter's Lodge, where he engages in conversation with Prudence. She asks Christian,

Saco Museum Panorama of Pilgrim's Progress

Prudence: Can you remember by what means you find your annoyances at times as if they were vanquished?
Christian: Yes:
--when I think what I saw at the cross, that will do it;
--and when I look upon my broidered coat, that will do it;
--and when I look into the roll that I carry in my bosom, that will do it;
--and when my thoughts wax warm about whither I am going, that will do it.

What a wonderful summation of how to remain on the righteous path, and so to banish carnal thoughts and wayward behavior!

Ken Puls wrote: [excerpted]

The conversation at Palace Beautiful continues with Prudence asking Christian some questions. Prudence represents our carefulness to walk in the wisdom and truth of God's Word. To be prudent is to live and act with discretion and to exercise good judgment. Prudence is the practical outworking of wisdom. Christian prudence is godly wisdom in action, as we apply God's Word to what we think, say and do.
Piety began the discussion by drawing out Christian's story and testimony for the benefit of all in the Palace; Prudence probes deeper. She presses Christian into a more weighty conversation that explores his inner motivation and struggles. Her questions focus on: 

1. His inward battles with former lusts
2. His fortitude to fend off carnal thoughts and worldly temptations
3. His strategy to guard his heart and mind against sin

I'll focus on the third question and excerpt Puls' notes here-

Prudence then asks Christian about his strategy to guard against carnal thoughts. What means are most effective in vanquishing besetting sin? 

Christian mentions the value of meditating on God's Word. He ponders the truth of Scripture and preaches it to himself. He anchors his thoughts in the promises of the gospel: the cross of Christ (the place of deliverance), the imputed righteousness of Christ (the coat he now wears), the assurance of salvation (his roll that he carries close to his heart), and his destination (eternal life in heaven). 

Finally Prudence asks him why he is so eager to reach heaven. Christian is anchored in God's Word and aiming for eternity. He has embarked on a journey and understands that this world is not his home. It is filled with sin, death, trials and afflictions, and it can wearisome as we press on day by day. We must remember that we are just passing through. Christian longs for the joys that await us in glory: 

There we will see Christ face to face (1 John 3:1-3; Revelation 22:4).
There we will be free, not just from sin's condemnation and power, but from its presence (Revelation 21:27, 22:3).
There we will have life eternal; there will be no more death (Isaiah 25:8; Revelation 21:4).
There we will be in the company of angels (Revelation 4:8) and the redeemed (Philippians 3:20) forever.

When you are discouraged...plagued by carnal thoughts...have sinned...drifted a bit...with ease and alacrity one can return to Jesus! Think of the cross, reflect on your salvation, look into the Book, and ponder your eternal destination.

That will do it.