In my study, I read an excerpt from one of my favorite books: Words to Winners of Souls by Horatius Bonar. You can read the book in its entirety here. One specific passage from the book I want to highlight is below.
"…when we can rest satisfied with using the means for saving souls without seeing them really saved, or we ourselves being broken-hearted by it, and at the same time quietly talk of leaving the event to God's disposal, we make use of a truth to cover and excuse a falsehood; for our ability to leave the matter thus is not, as we imagine, the result of heart – submission to God, but of heart – indifference to the salvation of the souls we deal with. No, truly, if the heart is really set on such an end, it must gain that end or break in losing it.
"He that saved our souls has taught us to weep over the unsaved. Lord, let that mind be in us that was in You! Give us your tears to weep; for, Lord, our hearts are hard toward our fellows. We can see thousands perish around us, and our sleep never be disturbed; no vision of their awful doom ever scaring us, no cry from their lost souls ever turning our peace into bitterness.
"Our families, our schools, our congregations, not to speak of our cities at large, our land, our world, might well send us daily to our knees; for the loss of even one soul is terrible beyond conception. Eye has not seen, nor ear heard, nor has entered the heart of man, what a soul in hell must suffer forever. Lord, give us a heart of mercies! 'What a mystery! The soul and eternity of one man depends upon the voice of another!' "