가랑비에 옷 젖는 줄 모른다
drizzle-IN clothing be-damp-PART line not-know-PRES
[Like] not knowing [about] damp clothes on the line in a drizzle.
“The little things add up over time.” That can be true about negative things or positive things, but clearly this is referring more to the negative. I wonder how closely it might correlate, alternately, with the straw that broke the camel’s back? I should ask someone.