... the most unexpected song/phrase/place would bring forth hidden memories of times long gone. This hurts.
... you're blinded and frustrated and angered by all the hurt.
... the memories of the beginning are almost unbearable because of all the promise beginnings hold... and knowing that some promises will and can never be kept. Maybe it's for the best.
... the guilt for all the things you did wrong can be debilitating.
... you realise that unlike Hollywood movies, sometimes there isn't an picturesque sunrise and a moment of utter understanding... an epiphany. Just a slow and eventual change in your thought process, heart and priorities.
At the end you move on.