We talk a lot here about sexual refusal, and it’s no secret I think that’s wrong and (almost) never justified. However, some guys need to grow up a bit over the issue of “not tonight”. Yes, I know that being told no when you feel the need/desire it like being told you are fasting because she’s not hungry. If that’s really the issue, you are hungry and she’s denying you what you need just because she does not feel like it, that’s her bad – especially if she says no often.
On the other hand, if you get a decent amount of sex, and she is really exhausted, or in pain, or has some other valid reason, then being upset about her saying no is like yelling at her for not cooking you a meal when she is throwing up sick. You wouldn’t expect her to cook for you in that condition, would you? [If you said yes, never mind, you’re too far gone! ;-) ]
The trick here is finding a balance between your needs and her needs. In a good, grown-up marriage, each person sometimes gives way for the needs of the other. Doing that requires a good understanding of the needs of your spouse. We all know what we feel, what we want, and what we need. If we have a good handle on what our spouse feels, wants, and needs, then we can make an intelligent decision when needs clash.
On her side of the issue: How tired is she? How bad does she feel physically and/or emotionally? What would it cost her to have sex with you despite whatever? On your side, how much do you need it? Is it “I’d enjoy sex”, is it “I need release”, or is it “I won’t sleep well if we don’t”? To make a fair decision, you each have to find ways to share your situation, and you each need to learn to hear and understand the other. Imagine putting your need on a point scale, with zero being no desire at all and ten being a desperate need. Imagine her “need” to not have sex also being on a point scale, with zero being willing if not desirous, and ten being “sex now would be torture”. With these two scales, the one with the higher number would “win out”. (Of course, a loving and mature spouse would bump their partners score a up point or two…) Can you really do that? Maybe, some couples do. It requires a great deal of honesty and trust, and you may need to work on those things outside of sex before you can deal with them in sexual issues.
You can modify/improve the above by giving her a variety of options to take care of your need. This also means you have to help her understand what you want/need on each occasion. Sometimes we want to make love, we want intercourse, and nothing else will really do. When that is the desire, then the offer of a hand or mouth is nice, but not acceptable. Even “I will lay here and enjoy you enjoying me” does not cut it at these times. Other times we are more about the pleasure, and then any enthusiastic sex act is appreciated. Still other times we have a desperate need for release, and on those occasions any sex act she is willing to perform is just fine. There are shades between all of those, and a few others besides. Many (most?) women don’t understand the range and variety described here – in part because most men fail to communicate it in a way women understand. Maybe what I have written here would help your bride – or be a starting point for you to explaining what you feel.
Other options, for some couples, are the man masturbating while with his wife, or in the shower with “her blessing”. I would save this for the “desperately need release” times, and if she indicates she should be able to do something the next day, do all you can to wait for that. As for masturbation, there’s a great set of posts, and some good discussion, over on One Flesh Marriage. See Take Matters into Your Own Hands, Masturbation: What’s a Wife to Do? and, Masturbation: A Little More Detail!.