when I had to cold turkey xanax, not by choice, for a few days after years of daily use it was hell on my body AND my mind. my body hurt like hell, I think the xanax relaxes your muscles when you're used to being on it and when it's stopped you're whole body freaks out. I was throwing up, had all the physical symptoms of opiate withdrawal plus mentally it's complete torture.
both opiates and benzos will cause your body to ache if you're dependent and stop suddenly. with benzos it's very dangerous to just stop so make sure you taper.
if you don't taper a heavy benzo habit you may end up having a seizure and then your muscles will REALLY ache, so be careful.
I don't think there is any long term damage once you've completed the withdrawal process, but I know it can take a long time to feel normal again.