You might think all XXXX's are one way (turns out you're wrong), but every person you meet who is an XXXX you push away thus you miss out.
or you maybe you think all YYYY's are one way (turns out you're wrong), and every person you meet that's a YYYY you draw closer and each one of them proceeds to piss on your life.
It is possible to simply not have an opinion on something or someone until you've gotten all the facts. You can still interact with people without sizing them up before actually getting to know them. Occasionally the environment will force you to make quick decisions with little information but in my opinion that should be the exception not the rule.