Over the last few weeks I've been reading J. C. Ryle's classic work Holiness. Chapter 6 is on the subject of growth in holiness, and in the middle of that chapter he says that one sure sign a person is growing in holiness is that he or she is growing in love. Putting the case negatively, he writes:
"There is no surer mark of backsliding and falling off in grace than an increasing disposition to find fault, pick holes, and see weak points in others. Would any one know if he is growing in grace? Then let him look within for increasing charity [love]."
Indeed, the more one grows in holiness, the more one becomes aware of the depth and horror of his own sin. And the more one grows in the awareness of his own sin, the more one becomes aware of the astonishing grace of God in Christ that has covered his sin. And the more one becomes aware of the grace of God in Christ, the less judgmental he becomes.
In this way, growth in love is tantamount to growth in holiness.