Performing Poorly on Mentor's Exam I was recently assigned a research mentor in my Master's program who also happens to be my professor (in a quantitative economics course). We've had a  brief meeting to introduce ourselves, and I made it clear that I'm very interested in his research subject; needless to say, I want to impress this professor. 

I just took the exam for his course which accounts for roughly my entire grade, and I did terribly. I studied a ton, but apparently focused on the wrong topics. At this point, I am wondering if I should somehow reach out to the professor basically telling him my thoughts of the exam, or if I should simply wait to hear from him, and if I don't hear from him, simply not say anything. He'll be my research mentor for the next year on this subject, so it almost feels like there is now an elephant in the room.
Would you recommend reaching out to the professor preemptively?
My advice is to reach out AFTER he has graded the exam (if needed).  This is for a few reasons.  


I have seen (and experienced) lower grades on an exam after a student told prof they had done poorly.  Teachers are humans and prone to halo effect bias.  If you did a bad job, let him decide that.  Don't do something to make him think that a priori. 
You don't want to exert (or be seen as exerting) any influence on the fair grading of your paper.  For example, that prof cuts you a break since you will work together.  (If you get that anyways, now, well...que serat.)  In theory, he is an inviolate Roman judge of fairness.  But in reality, teachers are people.
It may be seen, even accurately seen, as you being nervy, not strong.




If you hose the exam, then yes...talk to the prof about still having collaboration interest. Let him know your feelings.  But also be open to some real two-way discussion (even to include him saying "this would be a bad idea" or "let's see").