This has happened to me before and at least in my case the problem was everything else in my life. I learned that if anything is going poorly and I dwell on it I would loose focus on the other things/activities. At least in my case, it all became a matter of focus. I realized that there will always be some amount of stress in my life, be it work or family related, and that the key was to focus on the task at hand get through it and move on. I found that MA could be my momentary escape from reality if I could step away from the day to day and focus on the task at hand whether it was forms, sparring or whatever. This became clear to me when I finally achieved a long time goal at work which had been dogging me for weeks. That very evening, in my regular class I nailed a form that I had been having trouble with, it just seemed to flow and I realized that I was allowing my work related frustration to affect other areas of my life. I know this is alot easier said than done and it may not be the same for you, but maybe it will help. Good Luck