Adult children

What does a mother do and how should she respond as she watches her adult children make such poor choices. I feel powerless to teach anything...all I do is say that you are in my prayers. I have two a.c. who play around with drugs and alcohol. They speak to their father and me only when desperate or they have forgotten our last arguement. We all just play this little Drama. I'm so tired of it all. It zaps my energy so quickly, and I know my health has paid a huge price. I do my best to put them at the cross along with my pain. I try imagine that somehow, someway my pain will help encourage anothers walk who has similiar issues. It's like riding a rollercoaster. I think they are getting out of the woods, and then they turn around and go back for more garbage.
While Amanda and Josh were living with us I made it clear that they were to have no contact with Ashley because she would bring them further down. Now that Amanda and Josh have moved out...guess where they are? Yes of course...right back where they started. Unhealth attracts unhealth. Today I'm just throwing my hands up in the air. The drama in their lives is like one of those raunchy talk shows. They are all cheating on each other, using drugs and alcohol, smoking, piercing, etc...Just so lost! Because I know they have been raised well, (not perfect) but Well...it makes viewing thier lives so painful. They know where to find peace and joy yet they run to all this evil world has to offer. I must say that at this point there are no guarentees as to how your children will turn out. I have witnessed children raised in abusive homes turn out as well rounded individuals who contribute possitively to our society. I'm just really weary of their lifestyle. How much is enough? How can I just not care? Sometimes being a mom really stinks! I must lean on God for my pain, and stand in the gap for their pain...Can't believe anyone would choose the lifestyle they live in. I just don't get it! Any advice or thoughts on this would be greatly appreciated. Help.