Best damn decision you'll make all day, any day.
Brace yourself for the suck, because it's about to settle in for a little while. It does start to get better, but your body and your brain need some time to adjust, heal, and relearn how to operate without a bunch of cat turd essence coursing through your veins. Really make a point to capture and write out your thoughts during the highs and the lows of the coming days and weeks. That will help you to reinforce why you're quit and will make for good reading as you get farther down the road. You'll never want to repeat any of these early days again, so do it right and do it once.