People about negativity often tend to think is something people have in themselves. It happens, sometimes we 'feel' negative. But sometimes, negativity can be so deep into you, you won't even know it's there and 'realism' is actually pessimism.
Psychologically, we use the term 'reality is a mask of the negativity'. It's easy to rationalize that those people are simply 'realists'. They often presume the optimists are not realistic and are naive, and simply go with their heads against the wall. The question now remains, are those people 'happy idiots' or optimism is something else?
Well, the 'realism' of pessimist is incorrect. When you see the world from "realistic point of view", you can't help yourself not to be negative, IF your version of reality is negative.
If so, if your version of reality is negative, then you are restricted to believe that everything bad can happen - WILL happen. And all that good that can happen most probably won't, and will be the opposite.
Sometimes, this negativity is so deeply rooted in your subconscious, you wont be able to realize that you are negative person, and how would you tell that you are actually stuck in a field of negativity that will deny you of rationalizing 'reality' and believe that you (or someone close) will attract bad people, happenings, or feelings.