Generally speaking it is unlikely a couple ever wakes up one morning look at each other and says, "Lets stop having sex!" What normally happens is one person makes themself less available to the other. After enough rejection or excuses their mate (gives up). Some of them learn to live without it and others cheat or end the relationship/marriage. One of the dangers of being in any long term relationship or marriage is becoming so comfortable that you become more like siblings or roommates. Many people think that by desexualizing their relationship the love somehow deepens. Later they try and find ways to bring the magic back. "It's easier to maintain a fire than it is to reignite a spark!"
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