Chinese sentence — How to say “Thought of happiness would be forever, just like the unchangeable starry sky” in Chinese: 以为快乐会永久 像不变星空 。Yi3 wei2 kuai4 le4 hui4 yong3 jiu3, xiang4 bu2 bian4 de5 xing1 kong1. Also Without You – David Guetta ft. Usher. Lyrics on Screen

Chinese sentence — How to say “Thought of happiness would be forever, just like the unchangeable starry sky” in Chinese: 以为快乐会永久 像不变星空 。Yi3 wei2 kuai4 le4 hui4 yong3 jiu3, xiang4 bu2 bian4 de5 xing1 kong1.
Yi3 wei2 (verb, think or thought) kuai4 le4 (noun, happiness) hui4 (will or would) yong3 jiu3 (yong3 means forever, jiu3 means long, together they means forever and everlasting), xiang4 (adjective, is like) bu2 bian4 (bian4 means changeable, it is an adjective here, bu2 is a negate word, so bu2 biang4 means unchangeable), de5 (a particle to connect the attribute and the noun that it describes, here, the attribute is unchangeable, and the noun is xing1 kong1) xing1 (originally xing1 — noun, star, but here uses it as an adjective –starry) kong1 (noun, sky).
In this sentence, the subject is omitted, for this comes from a song — Starry sky / Xing1 Kong1 by a great Taiwanese band — Mayday 五月天 wu3 yu4 tian1
This song is written from the first person’s point of view, thus, what is omitted is the subject — I.
This is a theme song from a movie with the same title. It is a wonderful song albeit sad. In one of Robert Frost’s poems, it says “Nothing gold can stay,” however, life is just like the song lyrics “至少回忆会永久/zhì shǎo huí yì huì yǒng jiǔ/ At least the memory will be forever. See the song translation, check Chinese songs under the categories on your right side column.