OK, I waited on this one so you got some responses to put what I say in context.
I am a Chief and so I know a little about what it take to make Chief.
First off: Yes, your GPA might some day affect the orders you get, say instructor or prototpe duty, but remeber that there is a waiver for every thing and if you perfom well in the fleet you can get a waiver. AND I MEAN THERE IS A WAIVER FOR EVERYTHING!!!
Second: In the fleet work performance carries more weight than book performance (by far). Guys like you tend to be good workers. WHY? Cause you had to work your ass of just to get there and if you are doing about 45 hours a week studying plus class time you know what it is to put the long hours and hard work. Guy who fly thru school with little work are often surprised when they get to the boat and the work load is not impressed by thier GPA (valve maintenance is valve maintenance for the 3.9 guy just like the 2.6 guy! and no there is not a smarter way of doing it!!).
Third: Some guys (and gals, have to bew gender neutral you know!) are better at the hands on part such as in prototype and on the boat. In fact Nuc's a ntorious for being book smart and hand dumb, or lacking in common sense. Just cause you are haveing a hard time in power school does not mean you are doomed to struggle the rest of the way, but if you do contine to work hard and you control your own destiny!
Fourth and last: Even though this instructor went to the George Patton school of motivation! (he did'nt hit you with gloes did he?

). Rember Mr Jordan got cut from his high school basketbell team, Doug Flutie was to short/slow to be a pro Quarteback, Thomas Edison spent a year and a half failing before he finally got his improved light bulb (do'nt you even say he invented it!). Get the picture hard work is what it take to succed and you are doing it keep you the good work!! (this is what he should have siad to you!!)
Rob