NickLappos got it right, preparing too much can make your performance even worse.
A few weeks ago i had the opposite happen to me, had a normal standby duty when they called me at 5:00am and told me to go on a 12 hour duty to get my 6 months check done (fixed winger simulator, deadheading to and from, briefing time, 4 hours in the simulator). Of course i wasn't prepared since my check was only due the next month. I panicked a bit but then just got my stuff and went to deadhead to the simulator, met my captain for the day on the plane who was even more panicking since he was prepared to fly on the right seat (RTC) and had to fly now on the left one. Went into the simulator, the TRE gave me the choice to fly the check as check or just as assisting crewmember but i decided to have a go to get it done. Although i wasnt prepared, didnt study had no time to get my mind into the "check" status it was the best check i've ever flown so far.
Not studying at all is bad as well, but the ramped up studying before a check is due, trying to get the details with what TRE and what other crewmember you fly etc can make you enter the check in an already way too nervous atmosphere. Just flying the damn thing and trying to get it as right as on the line is the best you can try to do.