That's the title of this post, but I do not mean to restrict this little discussion to the workplace. The issue is that, wherever men and women congregate regularly, "chemical" attractions occur commonly.
These of course range from very mild to intense. It is difficult for people to focus on what they intend to do when there is a powerful attraction to a nice person of the opposite sex who is in regular proximity and contact. I have had people say to me "Is there anything you can do to help me get rid of this crush on so and so? It's messing up my workout/job/tennis game, etc."
A colleague and I were talking about this recently, and he (jokingly) suggested that people in that situation should just jump into bed together and eliminate the romantic/sexual tension and eliminate the mystery. "Get it over with. It's just biology." And of course their are rules about these things in the workplace.
In my view, such things are not necessarily a sign that a person is in a lousy relationship. Could be, but humans are designed to experience these things.
If a close friend confesses to you that some guy or gal at work or somewhere else is driving them nuts with desire, what would you say to them? Would you say"Grow up!"?