I will sometimes discuss problems I am having with my girlfriend, but if something is really bothering me I won't let on how much. Basically it's not a good idea to portray yourself as being weak in any way, because women like strong men.
I definitely wouldn't discuss any "self improvement" type of thing. As others have said it can kill the mystery and she may not understand your motives. My girl knows I work out for instance, but doesn't really know why. Obviously there are many reasons and benefits - she can use her imagination. She should see the end results of your self improvement, but not what goes into it. Instead, just have fun with her.