I don't think having a keen ability to anticipate potential problems has jack all to do with whether one's personality is optimistic or pessimistic. I'm an optimist by nature, but I have a highly refined ability to anticipate counterarguments (good lawyering) and the myriad ways that users can screw up an app (good programming). I don't expect bad things to happen, which would be pessimistic, I simply anticipate them and deal with it accordingly.

I also try to avoid correlating things that have no substantive connection to one another, like the bad psychoanalysis cited above.