첫술에 배부르랴 · 첫술에 배부를 수는 없잖아요
you can't expect perfect results right away; Rome wasn't built in a day (lit. would the first spoonful fill you up?)
Example
첫술에 배부르랴 하잖아요. 처음부터 잘할 수는 없어요.
You know what they say: one spoonful won't fill you up. Nobody is good at something from the start.
Word parts
첫술 is the first spoonful (술 'spoonful', as in 한술), and -랴 is an old rhetorical question ending: 'would one spoonful make you full?'
Good to know
Pronounced [첟쑤레 배부르랴]. Used to reassure a beginner, or yourself, after a disappointing first attempt.