Comment by dwringer

It may or may not be easy to fix properly, but if it's an inexpensive Seiko it may not be worth doing that, just replacing the movement when it wears out completely.

That said, simply adjusting the tick rate to regulate timekeeping is very easy and if you've got steady hands and a sharp eye then you can do it yourself with a wooden toothpick, assuming you've got a tool to remove the watch back. Any shop (offering repair facilities) could do it as well in a matter of minutes.