I have found that my definition of "functioning" changed to suite whatever stage of my alcoholism I was in. When I was younger I was "funtioning" if I could still go to class and work out. As I got older I was "functioning" if I could still go to work. As I got into my 30's I was "functioning" if I had never been arrested and still had my kids. At the end, I was "functioning" if I could just somehow not drink twice per week...
I firmly believe this is a progressive illness. The question is, what can I do to live life on daily basis happy and sober. That is where the 12 steps of AA come in....