Do I know you?

I'm sorry,
I thought I knew you
I didn't mean to stare.
Was that a smile of recognition
Just before that worried glare?
You're right, you're not the person
The girl I knew had hope
You're depressed and getting older
You can hardly seem to cope
She was young and full of energy
There was nothing she couldn't do
She had faith and joy and laughter
No, you're right. She wasn't you
Promise me if you see her
You'll tell her that I care
And I miss her looking back at me
From that mirror, over there