I don ’ t understand why you always look so happy , so energetic . It seems like you ’ Ve got good news everyday .   Really ? Do I look happy all the time ?   All I know is you look quite differently from other teachers .   Oh , do you know why ? Actually , it ’ s easy . Because I always exercise . My exercise , I think , is very hard . I often feel very good after conquering these difficulties . I feel alive !   Oh , I know . I saw you doing pull-ups one time on the campus and some students trying to imitate you .   Yeah , they are doing it for fun . Seldom would people like my exercise . It ’ s difficult and boring . 