Sounds like classic addiction. Ask an alcoholic why he picked-up a drink after long term sobriety and he will probably tell you the exact same thing you said in your post. I was talking to an alcoholic last week who, after 4 years of sobriety, was driving to his beach house and pulled into a liquor store. He got drunk and stayed that way for 3 years. Lost his wife, house and business. I asked him why did he do it, what were you thinking when you pulled into that liquor store? He said I wasn't thinking anything. I don't know why I did it, I just did. Very sad indeed.