As someone who's been under full anesthesia twice, I can definitely relate to the knotted-stomach feeling... It always seems fine from a distance, but when you're actually sitting in the waiting room or lying on your bed in the corridor, waiting to be put to sleep, it's truly a terrifying experience. "Someone will put me to sleep now and there's a small chance I may not wake up" is what usually goes through my head. It gives me the shivers to think about it even now.
And then you wake up and feel immensely drowsy and this pain thing keeps nagging at the edge of your consciousness (but that's ok, you can get an extra morphine shot and make it go away).
On the whole, I think the conclusion has to be: don't get yourself in situations which will require you to be operated (both of my surgeries were caused by things I had done).