This Song is taken from a very popular chinese drama called Together (当我们同在一起）which started broadcasting in December 2009 to January/Feburary 2010. In this video, the singer Kelvin Tan metions in the song that we always miss the stop of happiness. When we have the whole world, he/she cannot see, hence he wants to go back in time when the person is able to see and bring him/her to see the light of tomorrow. He also mentions about losing the world,he has a person by his side and he asks if he can go back in time and your dreams , the blue sky is called forever.