一口吃不成个胖子

比喻凡事都有个逐步发展的过程，不能立刻成熟、完善。也说“胖子不是一口儿吃的”、“那能一口吃成个胖子”。清·曹雪芹《红楼梦》第八十四回：“小孩子家，慢慢地教导他。可是人家说的： ‘胖子也不是一口儿吃的’。”

一口吃不成个胖子

比喻凡事不可能一下子就达到目的。

一口吃不成个胖子yī kǒu chī bù chéng ge pàng zi

noone grows fat on just one mouthful—nothing can be accomplished in one single effort (/at a single stroke); Rome was not built in a day;you must keep at it
❍ 小孩子家，慢慢的教导他。可是人家说的： ‘胖子也不是一口儿吃的’。(《红楼梦》1099) He’s only a child;you have to teach him slowly. As the saying goes，‘No one grows fat on just one mouthful.’

一口吃不成个胖子yi kou chi bu cheng ge pang zi

you can’t get fat on one mouthful(you must keep at it)