FEAR future events appear real
It is not a concentration camp from which you will never come back. It is a place that you'll come back from much better than you are.
You did not get sick a day and you're not going to get better in one either. Recovery is a process not an event. You will be in a safe place surrounded by professionals and others that are in the recovery process as well.
It is okay to be scared but this is the best possible thing that could be happening right now although it may not seem like it
Try to think of the wonderful life that you will be leading once the monkey of alcohol is off your back