You should anticipate being swamped every minute of the wedding week, and the wedding day is going to be such a whirlwind of emotions and new memories. The more preparation you put in early, the more confident you'll be when the mic is in your hand.
You don't need to memorize the entire speech word for word – but you need to know your outline.
Important to remember that you'll need to remain focused on the big day. If you do have a drink before the toast, I'd suggest you keep it to one.