The structure 一…是一…
The structure 一…是一… 
is only used in spoken language. It emphasizes that an action can be done gradually, step by step.
It is placed after a verb that denotes an action.
is only used in spoken language. It emphasizes that an action can be done gradually, step by step.
It is placed after a verb that denotes an action.Scheme
verb
一
…
是一
…
“一” can be followed either by a measure word by itself or a measure word with a noun.
Examples
你别管要做多少个题，做一道题是一道题
No matter how many questions you have to answer, just answer them one by one
nǐ bié guǎn yào huídá duōshǎo ge tí, zuò yí dào tí shì yí dào tí
我知道你因为生病而吃不了饭，但是能吃一块是一块
I know you don't want to eat because you're sick, but try to eat it bit by bit
wǒ zhīdào nǐ yīnwèi shēngbìng ér chībuliǎo fàn, dànshì néng chī yí kuài shì yí kuài
我也没做什么，只是过一天是一天
I didn't do anything, I just lived day by day
wǒ yě méi zuò shénme, zhǐ shì guò yì tiān shì yí tiān