A quote from Charles Spurgeon on backsliding:
Little by little, as a rule, backsliding leads on to overt apostasy and sin. No, no—so mature a servant of the devil as Judas is not produced all at once. It takes time to educate a man for the scorner’s seat. Take care, therefore, of backsliding because of what it leads to. If you begin to slip on the side of a mountain of ice, the first slip may not hurt if you can stop and slide no further. But, alas, you cannot so regulate sin! When your feet begin to slide, the rate of their descent increases, and the difficulty of arresting this motion is incessantly becoming greater. It is dangerous to backslide in any degree—for we know not to what it may lead.~Charles Spurgeon (Backsliding Healed 920)
It is a defiling thing to backslide, for a man cannot lose the intensity of his love to Christ and holiness without becoming thereby worldly and impure in heart. You cannot be less in prayer without being less like God. Sin is quite certain to seek a dwelling for himself in any heart where the Spirit of God is not actually present. Let your God withdraw His manifest fellowship, and sin is sure to come in to fill up the vacuum.