Everything about them says "this is the one for you!" You can't think of even a single thing you'd change about them. Every time you see them your heart pounds, and when there gone your always thinking about them. You won't fight because you'll have nothing to fight about them. And you'll love each other no mater what disaster falls your way.
You'll know in your heart without a doubt.
You don't you just have to assume, and hopefully it will be the right one
You don't doubt (in other words, you don't question anything, you just know that you know...) and no matter what that person does, forgiveness comes easy because of love.