PROVO President Gordon B. Hinckleys advice for teens to have fun by laughing, playing and dancing comes with a big BUT, Stan G. Crippen told a young audience Thursday afternoon at Brigham Young University Campus Education Week in a session called How to Be Happy Examining Your Expectations.Crippen, a teacher and educational consultant for REAL Educational Solutions, quoted President Hinckley from the Feb. 3, 1996, edition of LDS Church News: But there is a line in the sand which you cannot cross ever. There's a line in the sand which you cannot cross that pertains to morality, to honesty, to diligence. . . . Choose the right," he said.