Wow, that is a brain fuck question...

It boils down to a choosing to love someone. It is a total choice or decision.

You can say "I cant live without this person", but that is Bullshit. After you have had your heart ripped out and handed to you a few times, you come to the conclusion that you can live without anyone. It is true too, you can live without anyone.

It has to be a choice within you. A gift you give freely. Love is total acceptance of that person. Even all those things that you think are cute right now, but will in time drive you to insane.

The bummer is it leaves you vulnerable. It also means that at times you have to let go of the person and let them go to a better life.

In short I do not have a clue how you might know. I wounder if you ever can know.

But I am just a hopeless romantic.

I hope you find the answers you seek.