Ugh, this question could take forever to actually answer fully. I'm feeling lazy, so I'll just give the quick and dirty.

• there is no such thing as "the one"
• love is the strongest of bonds that you share with but one other person who means more to you than anyone else
• there is also no such thing "falling out of love"
• if your "love" can simply disappear, that is not love, but infatuation (or you realizing something about them that you cannot deal with)
• try not to be fooled by infatuation (yours or theirs)
• people can be an entirely different person when infatuated, and will likely be unable to properly see someone for who they truly are
• true fact: infatuation is the number one cause and killer of relationships
• it can be hard to counter this, even with objective thinking and taking your time going into a relationship

Other things to consider...

• you will get into some fights eventually, no matter how much you love each other. You'll get over it, though
• there are going to be things you really don't like, maybe even hate, about the one you love. Just think of it as the price of admission (as Savage likes to put it)

There's plenty more I could go on about, but is this enough?