personally, i never said "think positively"

just change your mindset.
think more negatively, if that helps, just:
Get Used To Dissapointment. REALIZE what REALITY is about.
there is NO pause function, NO rewind function, NO function whatsoever that will EDIT reality that has allready happened, so...
knowing this
what DO you get from lingering w past events? NOTHING
you must, not just know this, but truly REALIZE it. like a tattoo, it must be a fact of reality FOR YOU.
then you can move on, simply because you have no need to waste time and effort w lingering in the past.
I know that this post wasn't meant for me but I found it helpfull for a similar problem I'm have sometimes. Thanks.