You know how in the days leading up to a woman's menstruation the hormones and chemicals swilling around in there can be mood-changing. Lots of women experience little or no effects but sometimes these chemicals can be character-changing and turn a little angel into a serial kleptomaniac or mad axe murderer...
Not only do lots of guys have a similar thing going on, they also have a number of different values and different thought processes...
A guy gets used to getting sex or masturbating in a time frequency (that varies from man-to-man, his age and depends on individual circumstances) and it can seem, to him, as necessary as food.
The sex-urge in a man is like a lactating mother - as long as the demand is there, the milk will be available. If the demand is removed the milk will stop - but not straight away; there can be a very uncomfortable time lag... If demand is increased more milk (within reason) will be produced - again there is a time lag...
Some guys can't go without for more than a few hours before that uncomfortable time-lag situation begins to bite - the guy's balls begin to be sensitive and feel enlarged (even though they aren't), later his skin gets so sensitive he can feel his clothes and often a slight headache appears...
The psycological change that takes place is also interesting - women who the guy would usually find unattractive begin to look better and better...
Mother nature does her best to force breeding under any circumstances!
Not all men suffer in the same way or to the same degree and interestingly they rarely think about this or compare notes with other men - two of my friends, when I talked with them about this, also suffered in this way but kept silent as they felt there was something almost perverted wrong with them...
This is one aspect of the male physiology - like some women who suffer from serious pms this chemical overload can be character changing in some cases and has resulted in rapes and equally unpleasant stuff!
Then there is the male psyche - few men are naturally monogomous and many men are still the hunter/gatherer types who want to explore new country and scatter their seed over the next hill...
A lot of men do separate (sub-consciously) sexual activity from their emotional relationships because the sex act for them is physical and necessary (like food) and not an expression of emotional love. A lot of guys are completely baffled by the concept of sexual fidelity (for men) and the female reaction to infidelity is something that really has them confused...
Then you have the lack of maturity men suffer from - they can remain child-like in thought and deed for many years after girls have grown into women. I was 41 before adulthood began - some men never mature!
A lot of women know there are worse things to happen to a relationship than an occasional sexual adventure and if the man doesn't humiliate his partner in any way, is discrete and she isn't in any way deprived she isn't going to make an issue of it unnecessarily - as long as it isn't brought officially to her attention she can turn a blind eye...
They are also wise enough to know few men, especially young men, can resist that which is offered "on a plate" because they know the fellow's brain, at times like that, will be down there keeping his balls company...
It is hard work for a woman to prevent her man from straying - traditionally it is done by, once she has captured him, giving him as much sex as he can handle while making him fat and unfit - soon he will not wish to stray, become unattractive to other women or no longer able to stray...
While I have described a little of a typical man, there are lots who value (at any age or maturity) a good relationship, who wouldn't dream of having sex with a woman they did't love and who really do see sex as an expression of that love. Most of the remainder of men take many years to discover this...
There is yet another issue at work here - pornography! Overdoing the porno can be damaging - lots of guys and women begin to believe it is real and feel dissatisfied if their own sex lives don't match what they see on the screen. It is a fact many of the porn actresses (and actors) don't like anal sex - they do it for money and some of them need that money to pay for the corrective surgery later...
Porn is made by unscrupulous people in order to make lots of money and is not very often related to real sexual relationships - it usually based around plots involving casual sex and has nothing to teach anyone about real life! The actors in it are paid to look as though they are enjoying it!
As an occasional extra titillation to real life porn is fine but when somebody is drawn by habit or addiction to porn websites it is a recipe for trouble especially if masturbation takes place - masturbating to porn as well as having a healthy sex life is just likely to increase his libido when he should be trying to match his libido with your own...
As for anal sex: it is something nice to do sometimes for a change if you are both in the mood and it definitely shouldn't be conducted like a porn film - lots of patience, lots of lube worked right in with a finger or two first and take it nice and slow, shifting positions until you find the right one...
Be careful if he is well-endowed and careful also of the position used as anal sex traditionally has a lot to do with men doing things to women rather than men and women doing things with each other...
I hope this has given you food for thought...