You shouldn't drink alcohol. This increases the risk of failure.
You can take diazepam. Benzo is recommended. Unfortunately, I have no experience with benzos, so I don't know how you will react. It will most likely make CTB smoother. Although I don't know how much. If you have it and can take it, it will help. On this forum you can find threads on how much you should take.
It probably won't turn off the SI 100%, but it should make you calmer.
Additionally, it reduces the time to loss of consciousness (to my knowledge).