I am afraid to have a black-out
If you have learnt by experience that "black-outs" do not influence the outcome of your test, remember that fact. Apparently, you know how to deal with these unpleasant phenomena. Even so, worrying fantasies can suddenly hit you. These can take the form of predictions such as: imagine this or that happens. Disasters are anticipated, inevitably resulting in disagreeable feelings. With the knowledge you have acquired from comparable experiences in the past, you can correct these predictions. If you do so regularly, these fantasies will become less frequent.
Do you want to know more about black-outs? worrying in general?