Struggles With Sin No Cause for Distrust of the Savior; Rather a Sign of the Spirit's Work...

Indeed, so long as sin remaineth in the believer, he must, in order to grow in grace, have distress and comfort, either alternately, or both together; to the end that, when he is sorrowful, he may not be cast down too low, and that, when he is rejoicing, he may not be lifted up too high. 

Are Christ and God in Christ, together with his grace, mercy, and truth, as hath been said above, the primary grounds of a saints comfort and hope? I hence infer that, his manifold infirmities and deficiencies, in his exercise of grace and performance of duty, should at no time discourage him. Believer, thy remaining darkness, deadness, carnality, weakness, and indisposition of spirit for holy exercises, should indeed occasion in thy soul, much godly sorrow and self-loathing; but, they should never discourage thee in thy holy endeavours, nor cause thee to despond. They should not make thee distrust thy faithful Redeemer, or doubt of any promised blessing; because thy title to grace and glory, is not founded on thy own performances, but on the consummate righteousness of the Lord Jesus; and thy exercise of hope, should be suitable to the grounds of thy hope. Be not disquieted, then, though thou feelest the corruption of thy nature, strong and active; while thou findest, at the same time, thy renewed nature, striving in opposition to it, and mourning under a painful sense of it. Unbelieving discouragement, arising from a sense either of sins or of wants, of desertions or of temptations, will weaken thy hands, and indispose thy heart for spiritual obedience. It was when Peter began to fear, that he began to sink in the water.

Doth the Lord Jesus, usually afford inward and sensible comfort to his children, about the time of their first conversion? They may see in this, an illustrious display of his manifold wisdom, as well as of his redeeming love to them. One thing that he designs by this, is, that they may perceive as early as possible, the inexpressible advantages, that they have gained by the gracious change, which his Holy Spirit hath produced in them; and thereby be encouraged, as well as inclined, so to run the race that is set before them, as to attain the prize of inexpressible and endless joy, in his immediate presence. For, having marrow and fatness in their Father's house, instead of husks in a far country; spiritual and substantial delights, instead of pleasures that are carnal and empty; they cannot, even at the beginning of their Christian course, but acknowledge themselves already unspeakable gainers.

John Colquhoun. A Treatise on Spiritual Comfort