There is a deep connection between phobias, fetishes, and Obsessive-Compulsive Disorder. In each, someone has an emotion that threatens to overwhelm her. Or, she has a complex brain--so her own racing thoughts threaten to derail her.
In response, she compartmentalizes things in the outside world. A person with a fetish handles the monster of desire by focusing not on whole people but on parts--just a shoe, or the butt, or the slit in skirts. Focus on one thing organizes or restrains multiple feelings. A person with a phobia is similarly able to contain anxiety by condensing emotion to one target: She only fears spiders, or elevators, or crowds. The obsessive-compulsive mind works similarly: Faced with diffuse anxiety, she imposes a strict sense of orderliness on the outside world. She must separate her vegetables on her plate, organize her freezer with a color scheme, or sharpen her pencils to the same tip length.
I have a friend with a fetish that's a good example of the case. He is a controlling guy who can't stop feeling sexually jealous of the wife he's been with for ten years. When she made a cake for her officemates last month, he complained that she was trying to seduce a coworker. When she flirted with a waiter once, he went into a rage at the restaurant.
In the bedroom, only one strange scenario satisfies him. He likes to be faux-humiliated--or made a cuckold in the form of play. About once a week, the couple goes online to find a woman willing to join in their specific bedroom scenario. The scene is always roughly the same: The husband tries to seduce the new woman, but she rejects him. She says she'd rather have his wife. The two women engage each other, all along verbally berating the man, calling him "cuckold," "frat boy," "limp dick." The humiliation excites and satisfies the husband. But if the scenario ever loses the script--if the two women really do hit it off and stop "faux-humiliating" the husband--the husband gets angry. In that case, he is no longer being faux rejected but truly rejected. Overwhelmed, he has to stop the role play.
I've thought of that fetish in the same light as an obsessive-compulsive tendency. This is a man who can't handle his baseline feelings of shame--the potential to be humiliated, to lose his woman's love or his sense of control in real life. So he sets up tightly-orchestrated scenarios in which he can live out the "normal" human emotion of shame, to some extent. Here, he still controls the timing of the shame. He's the one directing it. He's the one who can turn it off. He can enter the real world through his own tightly-imposed organization.
I've recently heard a nice turn of phrase, which is that we do most of what we do to live within our "safety range." We each feel safe in different activities. Some of us feel safe when we're exercising physical power, even if that means jumping out of planes. Some of us feel safe in obedience. Some of us feel safe by maniacally compartmentalizing things that overwhelm us.
I wonder if you know of an anxiety you deal with through heightened orderliness. A friend recently gave me an example as easy as this: In graduate school, he always needed to clean his room before he started studying. He simply needed to impose some order on the external world, to make the mess of the internal world feel less like a mess.
I have some mild compartmentalizing tendencies, too: I need the gym every day as a scheduled release of anxious energy. I snack rather than indulge in big meals, controlling intake that way. I keep messy stacks of paper around the house, which I know the contents of pretty completely.