An interesting feature of any zero-sum game like jiu jitsu (a zero-game is one where every advantage you create for yourself must create an equivalent disadvantage for your opponent and vice versa - in short - the better you are doing the worse the other fellow is doing and vice versa) is that it creates very obvious opposing demands among the two athletes. Look at these two photos of the Ryan brothers in training. In one, Nicky Ryan plays bottom position against the formidable passing pressure of Georges St-Pierre. In the second, Gordon Ryan plays top passing game, utilizing one of his favorite methods, a body lock guard pass. You will see immediately the diametrically opposed interests of the two brothers based upon whether they are top or bottom position. When in bottom, our primary interest is in CREATING AND MAINTAINING SUFFICIENT SPACE TO MOVE INTO BOTTOM OFFENSE. As such, Nicky Ryan’s stance and posture is built around framing and extension to be able to move effectively under his opponent. Contrast this with top position, where the primary goal is that of REMOVING SPACE AND CREATING IMMOBILIZING WEDGES AROUND THE BODY TO FACILITATE PASSING THE LEGS OR, HAVING PASSED THE LEGS, PINNING THE UPPER BODY. You can see these totally opposed interests very clearly on these two photos. Once you see clearly that whatever is good for me must of necessity be bad for you, it is very clear what we each need to do in any situation (though be wary of fakes and feints that can take advantage of this kind of simplification). Always remember the very nature of the game - zero-sum where our respective interests run directly contrary to each other. This will answer many questions for the beginner when unsure of what to do in any given scenario.