I think what I'm most proud of with my time in PLTW is the Capstone project. Even though my groups solution didn't turn out exactly how we expected it to we worked very hard on it and were able to work through difficult situations as a team. To me the fact that we were able to do that makes me proud and gives me confidence for projects in the future.
For incoming PLTW students I would recommend really understanding how beneficial doing engineering in high school is for their future. So many education and life opportunities can come about from this class and if they appreciate that, then they will use this class to the fullest potential.