"Having said so much, let me now continue to think of the last two kinds of backsliders, and leave out the apostate. Let us first read his name, and then let us read his history—we have both in our text. The first part of his name is, “backslider.” He is not a back runner, nor a back leaper, but a backslider. That is to say he slides back with an easy, effortless motion—softly, quietly—perhaps unsuspected by himself or anybody else. The Christian life is very much like climbing a hill of ice. You cannot slide up, no, you have to cut every step with an ice axe—only with incessant labor in cutting and chipping can you make any progress. You need a Guide to help you and you are not safe unless you are fastened to the Guide, for you may slip into a crevasse.
- Charles Spurgeon, from the sermon "How a Man's Conduct Comes Home to Him", delivered on May 16, 1875, Metropolitan Tabernacle, Newington.
Nobody ever slides up, and if great care is not taken, they will slide down, slide back, or, in other words, backslide. This is very easily done. If you want to know how to backslide, the answer is leave off going forward and you will slide backward! Cease going upward and you will go downward of necessity, for stand still you never can. To lead us to backslide, Satan acts with us as engineers do with a road down the mountains side. If they desire to carry the road from yonder alp right down into the valley far below, they never think of making the road plunge over a precipice, or straight down the face of the rock, for nobody would ever use such a road. But the road makers wind and twist."
Therefore let us leave the elementary doctrine of Christ and go on to maturity, not laying again a foundation of repentance from dead works and of faith toward God, and of instruction about washings, the laying on of hands, the resurrection of the dead, and eternal judgment. And this we will do if God permits. For it is impossible, in the case of those who have once been enlightened, who have tasted the heavenly gift, and have shared in the Holy Spirit, and have tasted the goodness of the word of God and the powers of the age to come, and then have fallen away, to restore them again to repentance, since they are crucifying once again the Son of God to their own harm and holding him up to contempt. For land that has drunk the rain that often falls on it, and produces a crop useful to those for whose sake it is cultivated, receives a blessing from God. But if it bears thorns and thistles, it is worthless and near to being cursed, and its end is to be burned.
Hebrews 6:1-8 (ESV)