You might be a legit case of checkride-itis.

Since you probably have good piloting skills, here's an idea to deal with that: find an examiner who will give you the plan for the entire checkride on the ground and let YOU execute it in flight. Then you should try to ignore him and just conduct the flight. That way you're not getting distracted trying to interact with the examiner.

This worked for some non-aviation military training I used to do, haven't tried it in aviation.