Hello.

"... I know I've never really treated you right,
I've paid the price, I'm still paying for it every day"

Every, yes every, little part of Savage Garden's song "I Don't Know You Anymore" speaks to him.
He never took her seriously, he had her for granted, he fooled around, he dated and looked elsewhere, when all the while the person he really needed was there loving him.

Has realization come too late, he wonders.
Has she let go, for good.
He stares into space wondering if this could be one mistiming too many.