That a truly sanctified person is never in darkness, in one sense of the term, viz. condemnatory darkness; in other words, that he never loses the grace of a confiding trust in God and of solid internal peace, which his Savior has given to him as his inheritance, is undoubtedly true. If there ever be an exception, as for instance when the mental powers are depressed and darkened by the pressure of some physical disease, yet such exceptions are, probably, few in number, are explainable on principles peculiar to themselves, and are not to be regarded as essentially affecting the general doctrine.
But although those, who are wholly devoted to God, may be said always to have a solid and permanent peace, it is not true, that they are exempt from heavy afflictions both external and internal. On the contrary, there is some reason to believe, that those, who love most, will suffer most; that those, who are the strongest in the Lord, will have the heaviest burden to bear. "In the world," says the Savior, "ye shall have tribulation." "For unto you it is given in the behalf of Christ," says the Apostle in his Epistle to the Philippians, "not only to believe on him, but also to suffer for his sake."
It is important to understand this, to know that it is our lot and our privilege to be partakers of Christ's sufferings, so that those, who enter into the way of holy living, which is just what it is described to be, viz. a narrow way, may not be discouraged and overcome in the season of heavy trial. Satan will say to them at such times, Where now is your God? And it is exceedingly desirable, that they should know how to answer him.
— edited from The Interior or Hidden Life (1844) Part 2, Chapter 12.