The person misjudged quickly may require time you never planned to offer.

Snap judgements are cheap to make and expensive to correct. Deciding in ten seconds what somebody is like sets up an account you will then spend months revising, because every later piece of evidence has to argue against a conclusion you already reached. Most people never do the revising. They simply keep the first verdict and lose whoever was actually there.

If someone has surprised you lately, give them one deliberate hour rather than a reassessment on the run. And when you meet somebody new, try holding the judgement open a little longer than feels natural.