Varying your intensity : A truly vital skill in grappling is that of learning to VARY YOUR LEVELS OF PHYSICAL INTENSITY ACCORDING TO THE DEMANDS OF THE SITUATION YOU ARE IN. Probably the single most common problem I see in beginning students is an inability to change and regulate the intensity of their physical effort – they just go at maximum intensity the whole match. The inevitable result is that that quickly tire and fade. The other extreme is athletes who play so loose that when it's time to pull the trigger and hit a move, are so loose that it is simply ineffective. Somewhere in between these extremes is the happy medium you seek. As a general price of advice – only employ maximal muscle contractions in short and only when actually looking to perform a given move. At other times in a state of relaxed . Not that even in those short bursts of maximal muscular exertion – KEEP BREATHING and don't use muscular to compensate for positional errors – get your body in good position first and THEN apply your strength. In this way you can play a hard physical game without exhausting yourself to a point where you become ineffective. Look at this picture. Georges St-Pierre has gotten into a potential finishing position and is thus ready to apply some serious force – the strain shows. Next to him Gordon Ryan has gotten to a dominant position but does not yet have a finishing hold in place and so takes on a very relaxed demeanor. The contrast between them is and instructive – one situation demands muscular tension and exertion, the other allows relaxation on the understanding that this will preserve your strength for a time when it is needed. KEEP MONITORING YOU STRENGTH/TENSION OUTPUT AS YOU ENGAGE YOUR OPPONENT. Know when to be and when to be loose and you will defeat many opponents on endurance and the rest by having the physicality in reserve to finish that potential match winning move.