I don't get how I walked today, how I even got out of bed I don't

I don't get how I walked today, how I even got out of bed
I don't get how I talked today, when I feel worse than dead
I can't seem to understand how I got through this whole day
When knifes are rushing through my heart with every word I say
Or why I couldn't catch my breath when I saw you walking in
Or why we barely talk even though you call us friends
But hey, what do I know?I'm just the guy you left behind
Dumped from your heart erased from thought, out of memory, out of mind.