"Man, I'm so good at math. I got a 93."

Teachers, please answer:

Is it better to boost grades to inspire confidence in your subject or to leave grades undoctored to serve as a reality check?

Here are my thoughts on the benefits of each side (drawbacks obviously follow inversely...).

Boosting Grades:
Students like the class more because they think they are good at it.  They enjoy coming to class and would be more likely to pursue the field.  In math classes especially, boosting grades fights the I'm-no-good-at-_____ virus which spreads all too easily.

Not Boosting Grades:
Students earned their low grade by not studying/doing classwork/etc, so they have realistic feedback about their accomplishments; this reinforces (introduces?) the connection between effort and achievement.  Students also can't take the class lightly because they are either failing or not earning the grade they want/need.  Students learn that the minimum effort is not enough to pass.  The teacher gets a reputation for being tough, so students take the teacher's future classes more seriously.