NWGRITS: we learn the 3C's: you didn't cause, you can't control it, and you can't cure it.
There is also the idea of establishing Boundaries - firmly setting the limits that I will go to help so as to preserve my own well being. Addiction and alcoholism hurt both the drinker/addict and those around them. Friends and family get pulled into a swirl of broken promises, resentment, fear, and anger. I found that the best approach, as awful as it sounds, is to let the alcoholic know that I love them, but I will not sacrifice my own well-being to prevent them from harming themselves.
In fact, by establishing boundaries, I show sane healthy behavior. This is the one thing that may change the alcoholic - behaving rationally and with self-respect.
A relationship is a function of 2 people, a(me)+b(alcoholic)=c(our relationship); the only way to change the relationship is to change myself.