Why writing is like having sex when you're married

I've said this before, but I thought it would be worth explaining exactly what I meant.

You see when you first start writing, you kind of love it. You are in the honeymoon phase. When you are at work, at the gym (Ha! Me? At the gym?), wandering around the aisles of Tesco, all you can think about is doing it.
You get very excited at the thought of some alone time with your laptop (wahey!) and you plan ways of sneaking in a quickie session every now and again. I've been known to do it at lunchtime when the urge has been too strong.
And then, over time, you fall into a routine. You tend to know when the best time to do it is. (For example, forget about it on a Tuesday night when Desperate Housewives is on, or on Thursdays when Dr. House is tending to his patients.)
You know that a couple of glasses of wine definitely puts you in the mood for it, but that your results might not be the best in that state. It's always better to go into a decent session with a clear head.

Then, further in, when maybe you have children and other responsibilities, it can - at times - feel like a bit of burden. You do it out of a sense of duty and because there is something in you that refuses to admit you actually can think of better things to do with your time. You desire your passion for it back and will try different methods to increase your writing libido. Perhaps you'll read a good book, watch a good film, take a walk outside. Varying the routine and adding the surprise element can help. Going back to your first experiences, replaying them in your mind, can also help. As can taking the pressure off. Telling yourself there is no way you are going to do it is a sure fire way to get your brain craving a quick fiddle with your keyboard.

And then, you see, this is when it becomes most of all like married sex. You really can't be bothered, but you do it anyway. And you find you enjoy it. You find you lose yourself in it and let go of your inhibitions until you are battering away furiously, a feeling of exhileration flowing from your body.
And you wonder why you don't do it more. And you vow not to leave it so long til the next time, because as all good writers know, the more you do it, the more you want to.