We often think of organs are permanently destroyed by toxins - but the liver is pretty remarkable. If you drink more than 1-2 drinks a day - and then drop down to not drinking - your liver does actually repair itself. So even if you've been a heavy drinker in the past, it's worth it to give your body a fresh start.
The liver's a rather important organ, and the scary thing is, if you're destroying it you usually don't realize it until it's too late.
But if you're feeling fatigued, and you drink, it might be your liver warning you that it's being worn down.