Craving an emotional union
While the desire for sexual union is important to people in love, the craving for emotional union takes precedence. A study found that 64 percent of people in love (the same percentage for both sexes) disagreed with the statement, "Sex is the most important part of my relationship with [my partner]."
Feeling out of control
Fisher and her colleagues found that individuals who report being "in love" commonly say their passion is involuntary and uncontrollable.
For her 1979 book "Love and Limerence," the late psychologist Dorothy Tennov asked 400 men and women in Connecticut to respond to 200 statements on romantic love. Many participants expressed feelings of helplessness, saying their obsession was irrational and involuntary. According to Fisher, one participant, a business executive in his early 50s wrote this about an office crush, "I am advancing toward the thesis that this attraction for Emily is a kind of biological, instinct-like action that is not under voluntary or logical control. ... It directs me. I try desperately to argue with it, to limit its influence, to channel it (into sex, for example), to deny it, to enjoy it, and, yes, dammit, to make her respond! Even though I know that Emily and I have absolutely no chance of making a life together, the thought of her is an obsession," Fisher reported in 2016 online in Nautilus.
Losing the spark
Unfortunately, being in love usually doesn't last forever. It's an impermanent state that either evolves into a long-term, codependent relationship that psychologists call "attachment," or it dissipates, and the relationship dissolves. If there are physical or social barriers inhibiting partners from seeing one another regularly — for example, if the relationship is long-distance — then the "in love" phase generally lasts longer than it would otherwise.