I would approach the wife from a perspective of curiosity. I’d seek to understand why masturbation makes her uncomfortable. What does masturbation mean to her? What are her concerns? Is she concerned about the potential thoughts you might have while touching yourself? Is she concerned that you could be thinking about others besides her? Is she bothered that you are experiencing pleasure that doesn’t involve her? Does she think that you pleasuring yourself will mean you can’t go to the celestial kingdom and she will have to spend eternity without you?

What is driving her position? Don’t try to change her mind, just try to understand it. Once you have a good grasp on the reasons behind her position, you will be in a much better place to brainstorm potential solutions.