SAYING HOW WE FEEL
Have you ever told this person how you feel about their behaviour   Perhaps you should. That means sitting down together and sharing exactly what it's like for you. It would be good for you to share these feelings and it would be good for your relative or friend to hear you.

Tell them what it feels like to see someone that you care for slowly killing themselves.
Tell them how you feel when you see them intoxicated with drugs or booze.
Tell them how their using or boozing affects YOUR life - YOUR happiness.

SETTING BOUNDARIES
After we've shared our feelings, we can set boundaries. These mark our limits - beyond which we're not willing to go. Some boundaries like "no drink or drugs in the home" or "no borrowing money" can protect us a little, but they don't encourage the user to look for help. So, we might also need to say things like:

To a partner: "I can't live with your behaviour any more. Unless you get help, we'll have to separate."
To a teenager: "I don't need this. Unless you get some help you'll have to leave home"
To an adolescent: "You're behaving dangerously, I'll not allow you to go out until you agree to get help."
To a parent: "Look (mum/dad), your behaviour's crazy. Unless you get help I'll tell someone at school."
To a friend: "I don't enjoy your company now. Unless you get help I don't want to see you anymore."

And we keep to our commitment!
We must - for their sake and our own.