Two extracts from the notes accompanying Charles Spurgeon's commentary on Psalm 102, from The Treasury of David.
No man certainly commits sin, but with a design of pleasure; but sin will not be so committed; for whosoever commit sin, let them be sure at some time or other to find a thousand times more trouble about it than ever they found pleasure in it. For all sin is a kind of surfeit, and there is no way to keep it from being mortal but by this strict diet of eating ashes like bread and mingling his drink with tears. O my soul, if these be works of repentance in David, where shall we find a penitent in the world besides himself? To talk of repentance is obvious in everyone's mouth; but where is any that eats ashes like bread, and mingles his drink with tears? Sir Richard Baker.
Without faith we are not fit to desire mercy, without humility we are not fit to receive it, without affection we are not fit to value it, without sincerity we are not fit to improve it. Times of extremity contribute to the growth and exercise of these qualifications. Stephen Charnock.