It goes away... Your body will adjust and start doing the work again, it just takes time. Even when the meds are completely out of your system, your brain will need to relearn how to behave without them and do the job it's supposed to do in giving you the right chemicals. Some people's brains never did the job in the first place, hence the depression. ;)
Honestly, though, sertaline wasn't the worst med I've come off, but there was an SSRI I took for a short time when I was 18 that gave me horrible discontinuation symptoms. It took close to 6 months. But I think part of it, at least the mood part, was that the SSRI cut away a good portion of my emotions, and everything I had been too numb to deal with was still there. I wasn't doing any work, I was just hoping the pills would fix me, and it really doesn't work like that.
Now recently, less than a year ago, the advice my doctor gave me when I told her I didn't want to take pills anymore was to 1. Cut back slowly, 1 week at a time for a month. And then after I stop taking them, 2. Don't let myself suffer. If I need the pills, no shame in taking them.
For many people, I'm sure this is unfortunately true for most of us here, depression, and mental illness in general, is long road. If medication isn't the way you want to handle yours, then you'll need to figure out what really works for you that you can conceivably do for the rest of your life. Isn't that a lovely thought?