As he took one last drag on his cigarette, Xiaolei stared solemnly at the rain through the window. "I should never have touched it," whispered the

17-year-old. "I wish I could turn back time."

He was sitting in his room at a voluntary drug rehabilitation center in Beijing. After 15 minutes of silence, visibly lost in his thoughts, he suddenly murmured: "There are too many times I think 'I should have done this' and 'I wish I had done that' when I think of the past."