Re: is it normal to feel 'better' just before surgery?
Let me play devil's advocate. I don't think it is normal. Most people that get to surgical intervention usually fall in one of two categories. Either they have such significant pain it is interfering with their life, or they have some neurological deficit - like numbness, tingling, other disturbances, that require fixing. If this doesn't describe you then I would ask why are you proceeding with surgery instead of following conservative measures.
If you feel better, ask yourself if you have changed your activity level as you prepare for surgery. Did you rest more, stop exercising, something? Is there something that changed? If you feel much better, did the weather change where you live?
If you can't pinpoint anything and you really feel better, then you could also postpone and see if your particular case just needed more time and you are really starting to feel better.
The reason I say this is there is no gurantee that you will feel 100% perfect after surgery and if you are a case that is improving a little without surgery, then should you wait?
Or are you afraid and convincing yourself that you feel better?
Only you know your body.