I have this against you!

(Archibald Alexander, "Returning to Our First Love")

"Nevertheless I have this against you, that you have left your first love." Revelation 2:4

Declensions in vital piety are owing to a variety of causes, internal and external.
The whole, however, may be attributed to . . .
  the temptations of Satan,
  the allurements of the world, and
  the inbred corruptions of the heart.

Such declensions are very commonly produced by too much interaction with a careless, money-loving, pleasure-seeking world. Vital religion is a delicate plant, and being surrounded by many unfavorable circumstances, is liable to receive injury from contact with a polluted world. Worldly company and too much occupation in secular affairs, are almost sure to deaden our pious affections and to disqualify us for spiritual exercises.

He who is clothed in white and clean garments, will find it difficult to avoid contracting spots which deform and defile his robes, when he is obliged to live in a filthy house.

It is hard to pursue the world just as far as duty calls—and then to stop.
When the efforts to acquire money or property are successful, a pleasure is naturally experienced in the acquisition of such things. After a while, an undue love of the world is apt to be generated insensibly—and the evil creeps in insidiously.

But the undue love of the world, whether of its riches, its honors, or its pleasures—will soon injuriously influence the love of the soul to its Savior. The thoughts are too much drawn off from the contemplation of divine things, and the relish for spiritual duties and enjoyments is insensibly diminished. The duties of the prayer closet are no longer anticipated with delight; and the hours consecrated to private devotion, which used to be the most pleasant in the whole day, do not now afford the same comfort as formerly. The lack of enjoyment in pious duties, the wandering thoughts in the midst of them, and the lack of lively feeling—naturally tend to produce a backwardness to engage in them; so that were not the person forced, as it were, by conscience to enter his closet, he would often omit the duty altogether.

The most common means of restoring backsliders, is God's rod of affliction. The reason why God scourges every son who He receives, is that all have faults and imperfections, which a kind Father aims to correct by the use of the rod.

By affliction, the vanity of the world is seen—and the infatuation produced by the love of the world is broken. The backslider is filled with sorrow for having departed from the fountain of living water, and is driven to seek refuge and comfort in the mercy of our Lord Jesus Christ.