I really HATE when people say this.
I remember I had several deep discussions with one of my friends when he got married. He was the first of all of my tight core of friends to get married even though he had very little dating experience. I was fascinated. It made no sense to me so I HAD to understand, I NEEDED to understand. He hadn't been home from his mission long, he hadn't really been in a serious relationship, and here he was, getting married. I needed him to help me understand what he knew.
I have been in several serious, long-term relationships and never have I thought "That is the girl I WILL marry." Sure, I've though I could marry a couple of the girls. I'll admit it, I've never thought that I would marry Hannah, obviously, she wouldn't be in Canada right now if I had, but I've decided I could. I suppose hearing "You 'just know'." over and over again is messing me up a little, I'm sure I'm expecting to feel something unrealistic when I meet, or discover, 'the One.'
This all raises another problem for me. What about all of the people I know who 'just know' then get divorced 18 months later? Does this mean you some how have to "Just know you 'just know'."? Is 'just know'ing really that mistakable that you can 'just know' when you just don't? I've pretty much come to accept that I'll never 'just know' and I'll just marry someone who it makes sense to marry, kind of like some form of "a marriage of convenience." Since I have a thing for ambitious women I'll probably end up being in one of those long distance marriages, where both parties have good, promising careers and because of promotion, or whatever, they live in different cities and only see each other on weekends...
I guess the only time I've really ever 'just know'n about anything was job related. I remember my first night in the hospital, I should have been over-whelmed, I should have been stressed, I should have been wishing I could curl up and hide in a supply closet. But I was happy, there was no stress, I was calm, I knew at the time my personal state and feelings didn't match what they should have been, they didn't really make sense. So now I assume that is what people mean when they talk about 'just know'ing.