It depends what you mean by bad. There's painful, uncomfortable, unsatisfying, or just not as good as you'd like it to be. I don't believe any of these are reasons to end a relationship. The first thing you should do is talk about it. Figure out why its the way it is and then work together to change it. I agree practice is a good idea but research might help to, whether its a book store, a ,ahem, toy store or a porn site. And get out if the bedroom. Get a hotel room, take a cruise, or just go camping. Anything to break up the routine.