The liver doesn't always give "warning signs." I've seen a person with a cirrhotic liver that had no idea, no symptoms, until he came to the hospital for an unrelated surgery and it was discovered upon opening him up to take out his gallbladder. He had no idea. The only way to determine how much damage you have is to actually have a liver biopsy. Many people think that the liver will miraculously heal itself and turn into a fresh new organ as if nothing ever happened.....this is not the case.
If you accidentally cut yourself, your skin may "heal", but there could be a scar left behind. The same goes for your liver. Normal enzymes don't always mean that there is no damage.