I agree with what choc-mint mentions above. The issue with UWorld is that you become familiar and comfortable with the way the qbank tests you. Towards the end of the qbank you tend to develop a "feel" for the questions. The NBME practice exam questions did feel different from UW. However, their stems did not feel as long as that of the real test.
However, on the real test the questions may seem unfamiliar. Long question stems combined with test taking jitters can make the real test experience different. There is a distinct possibility that the test environment might be exaggerating my take on the real test. However, from perusing SDN many have a similar experience. In the end, you are being scored against others who most likely used UWORLD, NBME self assessments, UWSA as their primary sources during crunch time.
Time management and short memory span is key. You cannot dwell on your mistakes. Easier said than done! I had an incredibly hard time with this on test day. I finish with 15 minutes on the clock easy when I do blocks at home, but that is because I am comfortable making an educated guess at home. On the real deal I was cutting it close on every block. On test day, you have to train yourself, to move on. I would suggest that taking multiple NBMEs in a timed setting is the best way to prepare for this.
Caveat: Step2CK score pending (NBME4 @2wks out 250s, NBME3@4-5 wks out 220s), Step1 240s, MCAT mid30s