not giving a fuck is not a matter of how MUCH effort is put into something, but rather how much one CARES about whatever amount of effort they happen to have put into something.
For example:
man 1 can workhard all his life and make millions and literally be not giving a fuck about what has happened in his life
AND
man 2 can be homeless and mope and be sad about his position in life, therefore he fails in not giving a fuck and in this senario he is the "loser"
As opposed to the common misconception that man 2 gives less of a fuck because he hasn't worked a day in his life.
A sentence commonly used to express a feeling of utter and total disinterest in a subject, person, action or remark.
This phrase presents itself in real life most often under criticism...
#person1: Hey, you should stop scooping out the intestines of that badger with a protractor
#person2: I don't give a fuck
#person3: At least use a fucking spoon
Short-hand for the word floccinaucinihilipilification, meaning the estimation of something as valueless (encountered mainly as an example of one of the longest words in the English language).