I have, for better or worse, held intelligence above most anything else when it comes to choosing friends. Age doesn't really matter to me, as I am friends with people ranging from seven years old to over seventy. I avoid situations that would lead to the loss of any intelligence. This means that alcohol, which kills brain cells, is right out. It is so ingrained in my subconscious that I cannot even take a sip of alcohol without getting a bloody nose.
Addiction is something I abhor. That said, I will admit to the fact that I have become dependent upon a prescription medication in order to function in public. This does nag me, and unfortunately it appears that I will have to continue taking this medicine in order to function for the rest of my life. So, with that addiction, I strenuously avoid any others. Smoking, therefore, is ruled out.
Finally, illicit drug use. I have found this world to be far too incredible and filled with wonders to want any of it to be distorted, altered or destroyed completely. As interesting as they are, the works of Hunter S. Thompson fairly well provide the perfect argument against drug use as even the most strident D.A.R.E. program. The way I see it, Dr. Gonzo took drugs so you wouldn't have to.
I guess what I'm trying to say is this: You only have one life to live; why adulterate it with things that make you hallucinate, crave for more, and destroy your intellect?