I always worry when my pets get spayed or neutered. I am always pleasantly surprised when they are back to normal by the 2nd day. Duchess was back to normal on the same day as the surgery. In fact she was up and ready to play when I went to pick her up.
I had to put her in her expen to keep her calm. I did give her a half of dose of pain med that actually made her really sleepy. After her nap she wanted to play but I left her in expen and boy that's when the whining started. It was easier keeping her calm out of her expen.
I've been very fortunate in that all of my pets came through spay (all female pets) with no side effects.