WHO am I.......?

I don't know who am I.......??
My name is just my identity,
My behaviour is just my integrity,
But I still live in this world,
How is that possible.......??
Well, even I don't know,
Starting with HI,
Ending with BYE,
One day I realise,
Who I am.......
Everything has a definition,
But I don't.......
Stop running behind I,
Just live every moment of life,
You never know how each moment came and went,
It is better to enjoy them than to regret,
PAST is PAST, PRESENT is PRESENT and FUTURE is FUTURE,
But life is not a cakewalk,
So think about me instead............