You are not required nor expected to be perfect. In fact, the examiner wants to see you make mistakes so they can see how you deal with them. So if you screw something up, correct it as soon as you notice it, tell the examiner you weren't happy with your performance in that maneuver and ask them if they'd like to see you do it again. I had issues with my power and flap stall and compass turns so I did several until I was happy and the examiner didn't mind at all. Having said that, there may be several critical areas where you may not make mistakes and pass the checkride, so ensure you know what they are and you are confident you can nail them first time every time.
Good Luck!