What Is Fear?

Is it a necessity for living, is it a basic instinct that forms who we are, that defines us at times, and forms us at others, a development of us versus nature.

So is it normal to have fears, most people if not all will say yes, it is totally normal,

But what kind of fear? I mean there are types of fears, there must be, and there are also degrees of fear too,

So the type that freezes you in the middle of situations, is that good, is that occasionally good?? Is it categorized good at all? Or does it depend on the situation in the first place, and what about the kind of fear that prevents you from taking a chance, to leap into the unknown, is that good, occasionally good, is it categorized good at all?

And how about the fear that would make you think over your decision, over and over till there are no options left unconsidered, no possibility left unexamined, so that whenever something happen, it has already been thought of.

So now, which fear is okay, fear of the unknown, or fear of the known