the "IT" factor

I am haunted by years of English grammar for the usage "it." The vagueness this pronoun possess, indirectly refers to a previously mentioned subject, also known as an "anticedent" (see i still remember!). In any rate, upon determining greatness, I keep hearing that the person has to have this "it"-factor. All those episodes of "American Idol" or "Making the Band" where judges determine: this person's got "it."

What is this factor and quality that must exist? Several avenues blur past my mind as i think about "it."

I've had the unfortunate experience where a guy I was dating said ending our relationship stating that "it" wasn't enough. Sounds heartbreaking (and it was at the time), however, let's explore this ... must learn from your past to get to your future right? Right.

Now let's take how or why 2 people come together to formulate a relationship: they meet; they make emotional/physical connections; they become a couple. The "it"-factor delineates that a romantic relationship between 2 people is a combination of mutual attraction/respect, openness for a relationship, and a blinding trust in the other.

At times, there is the case in which all these factors appear to be in your favor: you are attracted to the person and you have a great time with them ... in fact, there's nowhere else you'd rather be. And yet, even you, know deep down something's missing: the "it"-factor. Some people are baffled by couples who seemingly aren't compatible or physically complementary are together, and they ask themselves, "how does that work?".
The answer is, "it" just works. We're not sure how, when or why ... but when you come across the person that belongs to you, you will just know "IT."