Using Breath to Improve My Tennis Performance
I am a decent recreational tennis player, somewhere between a 4.0 and 4.5 in the USTA ranking system. Over the past 3 years I have been concentrating a bit more on improving my game, but continually have the same problems with a lack of consistency, especially in my serve and backhand. Recently, I have started using a breathing technique based on 
the structure of the 6Dimensions RitualLog to control my game. Here's how it works:
Using my breath effectively
During a service game when I first take the ball in my left hand, I exhale for as long as I can, forgetting the point that just transpired, saying to myself "It's over, one point, win it." Breathing in, I step to the service line and go through two full cycles of breath while bouncing the ball, concentrating on my serve. On the second out breath I say to myself, "relax, rock, toss high" - because everytime I try to overhit the ball I tighten up, don't roll back far enough on my heels, and don't get my toss high enough.
When I forget to do this, I invariably miss my first serve. In a tight situation, I start thinking about double faulting, even as I'm breathing trying to concentrate. In this situation, I bounce the ball and breathe long enough until I am no longer thinking about double faulting, but visualizing the entry of the serve. When I'm really uncoordinated and tight, which happens all too often, I double fault - it's always because I didn't relax, rock and toss high.
Another breathing technique
The other technique I've been trying to employ is having a forceful exhale when my opponent hits the ball. This exhale does several things: it prepares me for what's coming, forcing me to move my feet, makes me inhale as I'm preparing to hit, which gets me ready to exhale as I stroke through the ball. I haven't yet figured out something to say to myself to help me stroke and not swing, but I'm working on it.
Review and Learn 
After every match or practice, I make detailed notes about what I did well and poorly. Before every match or practice, I review these notes while going through a short visualization exercise (found in the RituaLog). I am starting to discover some predictable patterns and my game is much more consistent now than it was just three months ago. It certainly helps to be playing on the beautiful red clay of Fluminese football Club here in Rio de Janeiro.
(A 6D note: Follow Chris while in Rio -at www.geostadia.blogspot.com)