Consecration therefore, as it seems to us, consecration without reserve either as to time or object, is the indispensable condition of inward religious advancement.
Whether, therefore, you have much religion, or little religion, or none at all, follow the divine light; whether it be the light of nature, which only shows us our state of condemnation; or the light of restoring and redeeming grace, which leads us to the Cross, that we may be pardoned there; or the light of that grace, which sanctifies the heart, by exploring its secret recesses and by bringing all into subjection; be it each or all, be it more or less, correspond with all your powers to all that is given, and God will give more. This, if we rightly understand it, is the law of increase in spiritual things, the law of light added to light, of grace, added to grace, of glory brightening in the front of glory.
We find here an answer to the question, often proposed with intense interest, why is it that there are so few cases of assured faith and hope? why is it that there are so few persons, who, under the influences of sanctifying grace, have reached the state of assured or perfected love, and of constant communion with God? The answer is, it is because by not corresponding to the light and grace which they had, they lost that, which they might have had. They would not take the cup of consecration, which they knew to be bitter to the natural taste, and therefore they did not, and could not receive the inward healing, which, in connection with God’s plan of operation, it might have imparted. It is impossible in the nature of things, that a person can have strong faith in God as a father and friend, or that he can love him with unmixed love, when he is conscious that by not consecrating himself he is violating a religious duty. Belief will always sink, and consequently love, which has its foundation in belief, will always sink in proportion to the weakness or defect of the consecrating act.
— The Life of Faith (1852) Part 1, Chapter 15.