South Park quote for graduation?

I am helping one of my friends write her valedictorian speech for graduation this Saturday and she is looking for quotes to use. I have loved south park over the years and have come to respect Matt and Trey as two of the most insightful people in the media and am trying to find a good quote from them either in interviews or on the show to go with the speech. It can be about friendship, education, the future, responsibility, or any other theme that could be associated with this period in life. Does anyone have any quotes that come to mind?