Very best of luck with it!! You’ll be in very good hands.
There is nothing to doubt once you’ve made your decision. I completely understand the decision to get rid of the monster sooner rather than later. So… don’t continue to doubt yourself. It was your decision based on the expert opinions given. It’ll be the right decision.
You’ve already been through a ruptured aneurysm so you know what that’s like. You can get through this just fine.
I’d say keep busy. There’s nothing to do between now and going in other than be packed, nicely hydrated, relaxed, know how you’re getting there, so if you’re kicking your heels and thinking about it a bit too much, find stuff to do. It’s like doing boring homework… all of a sudden other things round the house that you’ve never got round to could get done, maybe (as long as they are not big undertakings or too much to do) but might keep your mind busy. I’d say find stuff you need to use a bit of thought about as well, not things you can do and let your mind wander.
Let us know when you’re going in and when you’re safely through the other side.
Very best wishes