The thing about filing is not that your nails are too long. For some people the trigger for biting their nails is that they notice a piece of a nail sticking up far enough to be bitten. If they file the nails as short as they bite them, but completely even, then that trigger never happens, so they stop biting their nails.
Pretty much substitute filing for biting, because that looks nicer and is easier to modulate into something that does make sense.
The thing about filing is not that your nails are too long. For some people the trigger for biting their nails is that they notice a piece of a nail sticking up far enough to be bitten. If they file the nails as short as they bite them, but completely even, then that trigger never happens, so they stop biting their nails.
Pretty much substitute filing for biting, because that looks nicer and is easier to modulate into something that does make sense.