Bobular said:
Well...
Before any Matrix jokes, no, I ain't talking about Neo.
Damn it!
OK then, I'll be serious. I believe it's something you just know, but after some time interacting together, I don't believe in any 'love at first sight' stuff, you'll eventually come to the conclusion that you actually like being with this person and would like to be with them on a near permanent basis. If they feel the same way then they're the one, if not you become a creepy stalker and probably wind up in jail with no chance of finding your 'the one' unless they somehow managed to be incarcerated in the same facility, so get it right on the first time or else.
I think I slipped away from serious halfway through that.
...when I saw the title for this thread, my first instinct was going to be making a matrix joke.
Upon reading the first line of the OP, I was like "ugh, dammit!"
so, my backup plan was to start my original matrix joke, then quote the first line of the OP, and feign frustration...
then I saw your post... "ugh, double-dammit"
I fail at being an internet wiseguy today. XD
In the effort of contributing to the OPs intended topic, I don't really believe in the concept of "the one", since most people have personalities faceted enough to find long-term compatibility with any number of others, although the odds of finding one such person at random is pretty low.
I'd say, if the two of you can still enjoy being around each other after the first few months: when the brain chemistry that tricks you into passion because your body really wants to reproduce finally starts to die away, then you have a pretty sincere shot at making it for the long haul.