This is why people have to lock their doors, they can't trust someone just because they haven't seen them before. Not every stranger is going to put you on the evening news. Assume the best in humanity.
Assume the best of intentions in all people UNTIL they prove otherwise. Then mark them for who and what they are, and decide if they will be friends or enemies.
I assume the worst intentions of strangers and try to fight off the paranoid assumptions of even worse intentions of my friends.
I don't live a fun life.
I don't even have an idea about who I'd call my closest friends. There are the people I hang out with, but I don't know them well enough to always assume the best of intentions from them. I have maybe one friend I would trust completely.
I think this is probably more common than many want to admit. True close friends who have your back and do not judge you are hard to come by. Personally, my closest friend is my wife and there are times I don't share certain things with her because I know what the result would be. I don't trust people, therefore I will not share my deepest secrets with them. Acquaintances are a dime a dozen and they are fair weather friends - meaning, when the going gets tough, they will not be around.