My wife refuses to end her affair because she enjoys the sex too much. What should I do?

It is not true that desire cannot come back, but there are obvious challenges in your marriage, since there must be willingness to try from both partners. You are being remarkably stoical about this and I wonder why. Has your entire relationship been like this? If you can be patient, you might wait for her affair to lose its punch, but that would be painful and risky. Couples therapy could help, but if she won’t agree to it I recommend you seek individual therapy, as you clearly need support. At the very least, you could search for answers to why you allow her to call the shots.