Three general things:
Your writing has several grammar errors need to be refined (better paragraphing, and avoiding listing items (courses reasons) like you have did two places).
Your attitude toward topics should be very discussed more academic (refer to successful SOPs in your field to get ideas).
No promising that you'd do good (you need to show it by a past experience).
I have been applying to some PhD positions lately in O.R and learned things the hard way.
P.S. Had you been accepted back then? ;)