The nightmares I had were actually very useful when I figured out how to get to the core issues causing them. I used to have "using" dreams which were so real they terrified me and me think I had relapsed. It turns out that we can stop doing drugs and not be sober. There are plenty of other addictions, such as attention and people, that we can use to fill those voids. Once I realized what the problem was and discovered the source of that problem, I don't even think about using anything anymore. It's quite nice actually. :)