How do you know he's the one?

A friend asked, "How do you know he’s the one?"

She asked because as we all know, there’s always a possibility that things can fall apart in the future no matter how wonderful things are right now.

Well, I think I found the answer in the following statement,

“If the thought of not being with the person you’re with makes your heart ache, you figure out a way to make it work. You amend your plans. You change your vision of how you thought your life would turn out and you make a go of it.”