Discernment begins where first impressions stop being final verdicts.

First impressions arrive fast and feel complete, which is what makes them so hard to revise. Discernment is what happens after that first reading, when you hold it as a hypothesis rather than a conclusion and let further evidence actually count. Most misjudgments come from stopping at the first pass.

With the next person or situation you form a quick view of, write the view down and treat it as provisional. Look for one piece of evidence against it. That habit alone improves judgment considerably.