It's possible that some of your sadness is an involuntary reaction to jumping down to four units instead of eight. But, since you didn't have any serious physical symptoms from the change, hopefully your brain chemistry will level out quickly as well. During the first days of my most recent detox, I had crazy mood swings and occasional bouts of crippling anxiety. I wasn't even at the point of physical dependency, but my history with alcohol is etched into my brain, and starting back up and then quitting again was enough to mess with my brain chemistry. But, instead of letting it throw me into a tailspin of trying to chase away the sadness and fear, I talked to my sober support system, did some exercise, cleaned the house, and instead of setting off on a bender, I kept racking up sober days.