Self-flagellation

I was so unhappy with the way in which I lost this game that I decided to do a post-mortem and see where I went wrong (hence 'self-flagellation'). I missed all sorts of stuff, mainly due to a kind of blindness in my calculations - either not seeing that files were cleared or pieces freed by earlier moves, or simply ignoring my opponent's real threats by focusing on only one or two 'obvious' replies. I think I need to spend time working with middlegame positions in which there are many possibilities and concentrating on working through those possibilities as thoroughly as possible. Otherwise, I'm doomed to repeat disasters like this game. Time control was 15|10.