She might believe that if she blushes and she believes that she surely will her principal will fire her, because he believes she’s incompetent. Thinking the worst means Rosey believes that the worst will happen even though a much less disastrous outcome is more likely. Furthermore, when you think the worst, you might also believe that you can’t handle it. If you fail a test, you might believe that you’ll never recover from this setback. If you have a panic attack, you might believe that the intense and frightening sensations will overwhelm you.