White's only blunder in the game. This was the losing move if correct play did not follow. Black moves on to take most of whites pieces but good play holds out.

Calculating is something you learn over time. Sometimes the position is complex and you have to calculate a lot of different variations because your opponent can respond in multiple ways to your threat ( or you can defend in a multitude of ways to his ). Experience helps a lot in that case as you can quickly narrow down the 7 or 8 possible orders of capturing to 2 or 3. After that you just visualize what happens or here on gameknot, play everything over on an analysis board. The calculations/variations noted in the annotation are usually rather simple to make as the position isn't particularly complex. You take something with one piece, he captures with another, etc. you visualize everything until the sequence is done, then you go over it another time until you're sure you didn't miss anything. It can sometimes take quite a bit of time which you don't always have in an over the board game, but with experience you become faster. I also had some graphomotor issues when I was young, but of a different kind ( I coudln't draw between the lines, i couldn't use a sciccor very well, etc. ) but with enough practice and guidance I improved. In chess it's the same, you practice until you become somewhat decent at it.

Well it wasn't any serious real life stuff. But being in college things sometimes get more hectic then I'd like to admit. Procastination of a group assignement, a week filled with 4 presentations, social obligations, etc. I tend to avoid playing chess until those kind of things are resolved.