The current section I'm reading from Institutes is on faith. The following is lengthy, but I really enjoyed Calvin's assessment of faith and assurance of the believer.
Thus the disciples, while reprimanded by their Master for the weakness of their faith in crying out that they were perishing, still implored his aid, (Matth. 8: 25.) And he, in rebuking them for their want of faith, does not disown them or class them with unbelievers, but urges them to shake off the vice. Therefore, as we have already said, we again maintain, that faith remaining fixed in the believer's breast never can be eradicated from it. However it may seem shaken and bent in this direction or in that, its flame is never so completely quenched as not at least to lurk under the embers. In this way, it appears that the word, which is an incorruptible seed, produces fruit similar to itself. Its germ never withers away utterly and perishes. The saints cannot have a stronger ground for despair than to feel, that, according to present appearances, the hand of God is armed for their destruction; and yet Job thus declares the strength of his confidence: "Though he slay me, yet will I trust in him." The truth is, that unbelief reigns not in the hearts of believers, but only assails them from without; does not wound them mortally with its darts, but annoys them, or, at the utmost, gives them a wound which can be healed. Faith, as Paul (declares, (Eph. 6: 16,) is our shield, which receiving these darts, either wards them off entirely, or at least breaks their force, and prevents them from reaching the vitals. Hence when faith is shaken, it is just as when, by the violent blow of a javelin, a soldier standing firm is forced to step back and yield a little; and again when faith is wounded, it is as if the shield were pierced, but not perforated by the blow. The pious mind will always rise, and be able to say with David, "Yea, though I walk through the valley of the shadow of death, I will fear no evil: for thou art with me," (Psalm 23: 4.)
Good stuff. It almost makes me forget he was French. ;)