Being a Realist or a Pessimist

I have been told that planning for the worst is simply pessimistic behaviour. My gut feel tells me that I am a realist though.

Shouldn't one prepare for the worst, so that come what may, my mental, physical, economic states are ready for the situation? Would I rather indulge myself in fairytale endings and happiness, only to find that all these are unattainable?

Even if I take a middle-of-the-road stand, I will be ill-prepared for the worst scenario simply because I disallow myself to think about it in the past. In my mind, it has already been ingrained in me to always think and be vigilant to all such possibilities.

To me, it is simply the bottom line that when the worst case scenario floats up to me, I will have the backbone to face it squarely, instead of crumbling down as I most probably would without prior thought to it.

I may be wrong, since so many people have told me that I think too much. Some others have advised me that I will fall into the vicious cycle of thinking of the worst so much, that I fall into the big black hole of the worst happening simply because I innately already willed it to happen.

Maybe all the above is true...but I thought this is the whole concept supporting the insurance industry.