RedDog - So sorry got back later than expected. Firebolt has down a great explanation. Alcoholics need codependents and enablers. Codies and enablers help them achieve their goal of getting and staying drunk and maintaining their chaotic lives.
When I came here because my husband relapsed (I had only known him sober) it was pointed out to me that I was codependent. I firmly did not agree. My idea of codependency was buying him alcohol, or cleaning up a mess he made while drunk and I didn't do that.
What I came to realize is that I am very much codependent. I like to "fix" people. Just about every serious relationship I have had has been with people who have problems that I found intriguing and wanted to help them fix it (and never did).
What happens is you spend all your energy focused on the sick person and fixing them. I would say an addict of any sort is the worst choice of someone to fix. Slowly your life changes, you are no longer doing what you used to do because you are too busy trying to maintain status quo for the Alcoholic. You skip plans to go out because if you do you won't be with the alcoholic monitoring their consumption and making sure they don't burn the house down. You don't accept an invitation because you know your alcoholic will act inappropriately. On a day off you spend hours on a computer trying to find a way to make the alcoholic quit drinking instead of handling your own business. You talk to the alcoholic incessantly about getting help and may even get a positive response - only to see later that they do not act on what you talked about at all, and you have wasted another day trying to fix them while you own issues do not get attended to. Slowly your entire life revolves around the alcoholic. You choose your days off based on what they are doing. You schedule your life totally in order to "control" their situation in as much as you can - such as being sure you are available to drive them somewhere so they don't get a DUI.
In the meantime your own life spirals out of control, but theirs seems to be doing ok because YOU are spending all your time making it so. Depression, anxiety, insomnia, etc. all become part of your life and the more you do for them the sicker you become. The things that once brought you joy maybe aren't so much anymore. Work is exhausting because you are already tired. Friends are calling but its more annoying than anything because they are pressuring you to get rid of him and asking you to spend time with them but you don't have any time. You used to have a hobby that you spent your time on and now you don't because you are too tired and too busy fixing the alcoholic in your life to enjoy that hobby.
This is what I mean by getting sicker. Just some examples that may or may not be applicable to your life but I think you will get the picture.