For most the act of submission isn't instinctive. As humans we all want be our own person and not be told what to do all the time. From childhood, even infancy, we all push our boundries and test our limits. No one wants to be restricted. At least within the freedoms that are within government laws and human decency.
So what is it that makes submission to someone else in the atmosphere of sex, so appealing? Is is perhaps because in sexual passion we tend to let down what we desire, but don't want anyone to know about. In a dimly lit room, with the noise and hustle of the world, is shut off to us, this is where we are who we really are. Think, if you can't be honest with yourself, then you cannot be honest with someone else. And you certainly cannot be the keeper of your partner's secrets. But why hide behind closed doors? What is it about sex that turns the brain off and the body on?
If you want someone to give you anal sex, well then whether that be your partner or an instrument, then go for it, if your partner is willing. Don't be ashamed. The more that we hide these types of feelings and urges, the more disastorous things can become. I've heard on more and more occasions that the two reasons for divorce were sex (adultry, lack of sex, wrong kind of sex, etc.) and money. Why? Well because money sucks, but is a nesseciary evil. And, sex, because we don't let ourselves go. Adultry, affairs, brothels, prostitutes, and yes even mistresses, are here because people stiffle their true sexual desires. And that is not an absolute. There are I am sure some that go their seperate ways BECAUSE they don't share the same sexual preferences. But at least they were HONEST.
You will say I am shallow for this, but I found out myself personally. Honest discussions of sex with a potential partner, should be early and often. We like to think that we are more than most mammals on the planet, but no. We eat, sleep, and have sex. Just because the animals don't have to work, own a home, car, deal with money and politics, doesnt make them stupid. When we deny what our body tells us, like eating, it reacts. Granted stiffling sexual urges are not going to kill you (that's what masterbation is for) but they can ruin a relationship. If I had been honest from the start of my relationship then I would have been enjoying the fruits of honesty, since the start of it.
Sharing your sexual desires and plays are a great thing for a relationship. A great thing for two people who trust each other. Whether it be someone who you deeply love, or someone that just knows how to have a hell of a time. Be honest with him/her. You'd be surprised what people are surpressing out of fear of ridicule. There is a good rule that you can basically learn someone's sexual secrets . . .
The more rigid someone is the more they are keeping to themselves.

be honest and you'll be plesantly surprised
Eternally . . . Her_Slave