For Reasons Unknown

A person leaving his wife/girlfriend, because he lost his love for her and doesn't know why.
The packing the case thing his him leaving and the 'I look alittle bit older' thing is him realizing the stress is making him look older.
'one deep breath' 'one big step' 'moving a little bit closer' is him leaving and being scared.
'The open chair' could be some consuling or something trying to find out why he lost the love.

I always picture someone realizing they have changed in a matter that they don't feel the same about life or like they don't love someone like they used to and wishing it wasn't like that.

It's about being in love waking up one morning and although nothing physical has changed and the world is still the same, you don't feel the same but you want to fight for it and "Breathe that fire again!"   :)

http://www.thekillersfansite.com