tirer des plans sur la comète bedeutet auf Englisch

bite off more than one can chew▼(To try to do too much)
verb
[UK: baɪt ɒf mɔː(r) ðæn wʌn kæn tʃuː] [US: ˈbaɪt ˈɒf ˈmɔːr ˈðæn wʌn ˈkæn ˈtʃuː]

build castles in the air▼(to have any desire, idea, or plan unlikely to be realized)
verb
[UK: bɪld ˈkɑːs.l̩z ɪn ðə eə(r)] [US: ˈbɪld ˈkæs.l̩z ɪn ðə ˈer]

reach for the stars▼(to have high hopes)
verb