Who am I?

Who am I? ‎'I' am HIS and HE is 'mine ' is as per my Sufi connotations. But I haven't yet deciphered it. The heart is still waiting.

I am that
you are That
That is That
and That is what is forever

Are we part of that forever, or are we playing just a part?
As an intrigued child, I would ask my grandfather, where Allah lives. I use to wonder, from where these snow flakes and rain drops come. And my grandfather would say, 'Allah lives in your heart'. May be it was a shrug off theory used by him, as I used to pester him with obnoxious questions. However, years later, a fairly religious friend of mine asked me, 'where does Allah live'? (He took my religious understanding for granted: I don't blame him). And without battling an eye lid I replied, 'HE lives in our hearts'. I could actually understand, at the every moment, what my grandfather meant. It may sound ordinary, but it was quite a significant moment in my life.