A relaxed body moves better and moves longer than a tense one: Jiu Jitsu is a combat sport – so its only natural that you should physically tense up when the action begins. Be aware however that excessive physical tension is a potential pitfall that has sent many of us into early exhaustion and failure. Keeping a loose and relaxed demeanor whilst grappling in a competitive match is a difficult thing to do. Moreover, we can't be loose all the time. There are times when maximal tension may be needed to finish a move. In addition we don't want to be so loose that you flop around ineffectively. Finding the right amount of tension vs relaxation at the appropriate times is a long term study. Understand however, that it's an IMPORTANT study, as your ability to relax when you can will be a BIG part of what determines your endurance in long tough matches – much more so than your cardiovascular fitness level. Start out by learning to relax yourself whenever you disengage with your opponent. Then start to expand upon this by learning to relax when caught in a pin or inferior position. Then try to get more relaxed even in the neutral positions so that you spend the majority of a match in a relatively relaxed demeanor. Soon you will notice your ability to move fluidly in response to your opponent's movements improves, along with the length of time you can engage with a tough opponent. Look how relaxed Nicky Ryan looks as he enters a training partners open guard – getting to that level of relaxation in sparring takes time, but the potential benefits make the effort worthwhile