They Know Themselves Best Who Fear Themselves Most

Patrick Walker, Six Saints of the Covenant, ed. by D. Hay Fleming, Vol. 2, p. 41 ('Donald Cargill's Life'):

He preached upon that word in the forenoon [June 1681, one month before his death], 'Be not high-minded, but fear' [Rom. 11.20]. His first note was, that these who knew themselves best would fear themselves most; and that, as it was to determine what a length a hypocrite may gang in the profession of religion, it was as hard to determine what a length a child of God may go in defection, having grace, but wanting the exercise thereof; and that a Christian might go through nineteen trials, and carry honestly in them, and fall in the twentieth. 'While in the body, be not high-minded, but fear.'

Maurice Grant, No King But Christ: The Story of Donald Cargill, p. 172:

Concluding his exposition, he went on immediately to give the first of his two sermons. It was from Romans 11:20: 'Be not high-minded, but fear,' and was a characteristic study of the Christian life, drawing richly on his own experience. 'Those who know themselves best,' he declared, 'will fear themselves most: and as it is hard to determine what length a hypocrite may go in the profession of religion, so it is hard to determine what length a child of God may go in defection, having grace, but lacking its exercise. A Christian may go through nineteen trials, and carry honestly through them, and fall in the twentieth.' Cargill made it clear to his hearers that he was speaking here of those who were true Christian,...