I just messed up my exam because I used the wrong value in wrong problem since teacher didnt had it on the test and just annouced it in the class instead of writing it on the board. This cost me 20 points and a letter grade. In the past, in some classes I have really screwed up the first test but then pulled my grades and ended up with B+. Do you make these stupid mistakes that end up costing you dearly? I wonder how some people can maintain their 3.8 GPA.