Social Security benefits while working

I have been thinking about retiring lately, but with my bills, the amount I could receive simply would not be enough to get by on. I'm certain this applies to many of you out there.
I would still have to continue to work and would surely pass the 15,700 dollar limit.
I realize that after that limit is reached every thing I make over that would reduce my benefit by $1 for every $2 earned.
My question is by what mechanism do they do this? Does the actual amount of the monthly benefit decline as I make more or is the entire benefit cut off after a certain amount over the $15,700 is reached?