You should cry all you want to, and then wipe the snot off your nose and tell yourself you are doing well, and take it day by day.
Surgery for me is a really traumatic thing (long stories based mostly on me never reacting to meds they way they anticipate) - so I was really scared of not waking up, and waking up the wrong way (i woke up in the middle of a knee surgery once).
Your fears are justified, just be sure the way you react to them is reasonable to your emotions, but aimed at your goal.
So much good luck to you! God bless.