John Newton 1725-1807
John Newton was an English sailor and later captain of ships in the slave trade. His mother gave him christian instructions early on, but she passed away when he was 6 years old. As he grew up he lost all his christian upbringing and followed his dad into the seafaring business and became a sailor without any scruples or morals. On one of his trips back from Africa his ship got almost totally shipwrecked and many sailors lost their lives and his family gave him up for dead, because they were out to sea for more than 18 months. But God used this to draw him to himself and he converted and little by God's glory!
He is the composer of "Amazing Grace" and many letters and writings​ 
In his old age, when he could no longer see to read, John Newton heard someone recite this text, "By the grace of God—I am what I am." He remained silent a short time and then, as if speaking to himself, he said: "I am not what I ought to be—ah, how imperfect and deficient! I am not what I wish to be—I abhor that which is evil, and I would cleave to that which is good. I am not what I hope to be—soon, soon I shall put off mortality, and with mortality all sin and imperfection! Though I am not what I ought to be, what I wish to be, and what I hope to beyet I can truly say, I am not what I once was—a slave to sin and Satan! I can heartily join with the apostle and acknowledge, "By the grace of God—I am what I am!"
By the Grace of God I am what I am!
Every man's shoes should be exactly of one size!
The church of Christ is composed of all who are savingly united to Him by genuine faith. They are infallibly known only to Himself. They are scattered far and wide, separated from each other by seas and mountains; they are a people of many nations and languages. But, wherever their lot is cast, they hear His voice, and are under His gracious eye. They do not have equal degrees of spiritual light, or measures of grace—but they are all ‘accepted in the Beloved'. They are all spiritual worshipers, and joint partakers of grace—and all will hereafter appear together at their Savior's right hand in glory! In whatever is essential to their salvation, they are all led by the same Spirit, and mind the same things.
But at present they are in an imperfect state. Though they are new creations—they are not freed from the 'principle of indwelling sin'. Their knowledge is clouded by much remaining ignorance; and their zeal, though right in its aim, is often warped and misguided by the corrupt influence of SELF. They still have many corruptions. They live in a world which furnishes frequent occasions of enticing them. And Satan, their subtle and powerful enemy, is always upon his watch to mislead and ensnare them!
Besides all this—they are born, educated, and effectually called, under a great variety of circumstances. Habits of life, local customs, early relationships with families and friends, and even bodily constitution, have more or less influence in forming their characters, and in giving a bias and turn to their manner of thinking; so that, in matters of a secondary nature—their sentiments may, and often do—differ as much as the features of their faces! A uniformity of judgment among them on these secondary matters is not to be expected, while the wisest are defective in knowledge, the holiest are defiled with sin, and while the weaknesses of human nature, which are common to them all—are so differently affected by a thousand impressions which arise from their various situations.
They might, however, maintain a unity of spirit, and live in the exercise of mutual love, were it not that almost every individual unhappily conceives that they are bound in conscience, to prescribe their own line of conduct—as a standard to which all their brethren ought to conform! They are but few, who consider this "narrow mind-set" to be as unnecessary, unreasonable, and impracticable, as it would be to insist, or expect, that every man's shoes should be exactly of one size!
Thus, though all agree in asserting the authority and right of the Lord Jesus, as King and Head of His church—yet the various ideas they frame of the rule or standard to which He requires them to conform, and their pertinacious attachment to their own conceptions of it—separate them almost as much from each other, as if they were not united to Him by a principle of living faith! Their petty differences form them into so many separate churches; and the fury with which they defend their own ideas, and oppose all who cannot agree with them in every minute point, makes them forget that they are children in the same family, and servants of the same Master! And, while they vex and worry each other with disputations and censures—the world is bewildered by all this, and laughs at them all! The spirit of love is restrained, offences are multiplied, and Satan is gratified by beholding the extensive effects of his pernicious and long-practiced maxim, Divide and conquer!
"Accept one another, therefore, just as Christ accepted you, in order to bring praise to God."     Romans 15:7

You can find a lot of his writings at;​