What is the difference between passing judgement or warning someone? For instance, let me present the black and white examples:
Judgement: Because you took a wrong turn, you fell off a cliff.
Warning: If you take the wrong turn, you will fall off a cliff.
In my opinion, judgement should never be necessary, instead a warning will suffice.
In ethical terms, this means that you should warn people against potential dangerous, illegal, or amoral decisions before they make them, but not judge people for the mistakes they have made unless they knew the consequences and accepted them nonetheless, and are not remorseful.
In theological terms, you are never damned until you make the final mistake before you can repent and make amends. Basically, don't walk away from God right before you die. Be repentant always. Otherwise you may very well be damned, not by your sins you've commited, but the ones that you will commit.