my weird superstition

I have been getting dizzy a lot lately... that is to say twice in the last two days I have felt dizzy for no good reason, so my first thought was... "well it must be a brain tumor" because that is usually my first diagnosis for any sort of unusual aches, pains or symptoms I experience, but I have this weird sort of superstition where I kind of believe that if I acknowledge that a scenerio is possible, it won't actually happen because I am kind of prepared for it... I guess it's kind of like a reverse murphy's law... like I try to think of the worst case scenario for a situation and then I kind of figure since I am just a person with no particular medicle or worldly knowelege if I can concieve of something happening with no outside consultation, there is no way in hell that it will actually happen because I am just not smart enough to accurately diagnose things... although that being said I kind of feel like maybe I am getting too cocky in thinking that I'm safe from things just because I think that I can't diagnose myself... is that an oxymorone?