Fitness and Chess
I took a bit of hiatus from chess, perhaps three months with no serious play, and, upon my return, I found that a lot of things that had been floating around half understood in my mind had cemented and my rating increased by about a hundred and fifty points (my new peak was over 200 points above my previous rating but proved unsustainable).
Another factor that I feel is definitely influencing my chess would be working out. I understand that it can take two months (or even longer) to start to see the changes in your physical form when you start lifting weights, but I started to see benefits to my chess game immediately. Aside from stamina and some benefits to self confidence I attribute an increase in the clarity of my thoughts as I considered variations and a definite increase in focus. These mental benefits came much more quickly (within a couple of weeks) than the physical changes, and, in many ways, are more rewarding.
In addition to lifting weights I've started walking about a mile a day, five days a week (to and from classes really; I work full time and commute to full time school) and instituted a more regular diet (scheduling carb heavy meals to coincide with workouts and periods of physical stress and protien rich meals (low in carbs) for the other times). These changes and green tea on a regular basis have me feeling better than I have in years (physically anyway) which is interesting considering my stress levels are much higher this semester than they have been in recent years.
I would heartily encourage others to do as I have done and start exercising... not only will you feel better but you might gain some of those coveted rating points...