22 And it came to pass that from this time forth there began to be lyings sent forth among the people, by Satan, to harden their hearts, to the intent that they might not believe in those signs and wonders which they had seen; but notwithstanding these lyings and deceivings the more part of the people did believe, and were converted unto the Lord.
(3 Nephi 1:22)
How did Satan send forth these lyings and deceivings? Through people, of course. There were cynics among them, as there always are. However, the sign they had all experienced was so vivid that most of the people were able to ignore the foolishness and focus their minds on the uplifting message of the gospel.
I sometimes find myself gravitating to cynics, partly because I find them funny and partly because they come across as being intelligent. I would be wise to focus my attention on people who are building things, not on people who are tearing things down. Cynics might have useful insights at times, but their habits of mind are destructive. I should consciously focus my attention on those who are committed to achieving good things, not on those who are constantly finding fault.