Trying endlessly to gold License B-3 (del Sol into the hairpin at Deep Forest, I believe) is one of my worst GT1 moments. I wanted to gold all the Bs so I could win the prize car: a Dodge Concept. I wanted this car in particular because I wasn't getting anywhere with the Hard Tuned series, and so I figured the Concept would be a great automobile to drive.
I finally gold all the Bs, after spending hours at B3. And then *cringe* I learn the Concept can barely be modified beyond its stock horsepower!
All that time ... wasted. It probably helped me in the long run, though. Somehow.