Proverb: 가랑비에 옷 젖는 줄 모른다

Literal Meaning
You do not realize your clothes are getting wet in a drizzle.

Usage
Often used when you realize that you have nickel-and-dimed yourself to where you have no money left.

English Equivalents

Many drops make a flood.
Many a little makes a mickle. 

Little strokes fell great oaks.

Vocabulary

가랑비에 옷 젖는 줄 모른다

가랑비 - drizzle, sprinkle  

옷 - clothes
젖다 - get (be) wet (drenched), get damp, get moist, get soaked
모르다 - do not know, do not understand