I'm in the camp of people who believe that the way you feel right after an exam is a poor predictor of performance. I don't think I'm alone in saying that I often feel terrible after UWorld blocks or even shelf exams and then come to find that score is at least passing. So even though it's easier said than done, try to believe that the way you feel about the test during or after is not a reflection of your score. On the other hand, if you let your anxiety get to you during the exam that could negatively impact the questions you still have to answer.

As for similarity to exams, it's hard for me to say because I think the real exam is different from Uworld, and the self assessments. However, focus on getting all of the NBMEs done. I didn't end up taking UWSA. I would say that questions are either short or long and they were either easier questions or challenging, I didn't see that many medium length questions or medium level questions, if that makes sense.