Fair enough, though it is common knowlege.
Yes, I am simplifying a little. I don't write a book on my philosophy of life everytime I answer a post.
But since you want clarification, clarification you shall have.
Threat does not equal fear. That's a good place to start. Threats are not to be feared, but dealt with.
Everyone is a potential threat until you know they are not. You have no idea who is a thug or child molester and who is trustworthy, until their actions reveal their intentions, until time-in-contact reveals their character. Trust is earned, never given.
Everyone that approaches you wants something... don't trust them until you know what it is, and be aware that their first stated reason is often a lie. What they want may be innocent enough... a moment of your time, some company and conversation for a short while... or they may want to con you, use you, or victimize you... or worst of all, they may want to sell you Life Insurance.
Fear no one but keep an eye on anyone whose trustworthiness has not been thoroughly proven.