How do I stop being so afraid of people?

I journaled and theorized about it for years—now I need to just get out and do it. But we all know it’s dangerous out there—mixed in (often imperceptibly) with positive people and situations are toxic, sneaky, opportunistic, and sad/scared/just plain mean ones. That’s what’s kept me from really moving forward, but I’m done with being a prisoner in my own life and screwing up opportunities that do come my way. How do you let down your guard long enough to determine whether someone/something is any good for you?