Sometimes you have no other choice than to abandon your standard game plan when facing opponents of a larger size or superior skill. Some attacks or defenses will simply not work and you have to adjust accordingly.
In recent history, say the past year or so, every class I am paired with opponents who outweigh me by 30 to 50 pounds married to more experience. I do not learn much in the 5 minutes of attack defend, but the hours spent on reflection has taught me much. And my game has improved vastly because of this as well as my strength and conditioning. Of course my opponents have improved as well, so the results of each match has not altered much, but is closing in on parity. Time will do this as everyone improves.
I have learned when fighting a stronger and larger opponent, it is far more difficult apply different arm bars where strength is required. Try an Americana from top half guard against a guy who outweighs you by 50+ pounds who can most likely beat Sylvester Stallone in an arm wrestling match... You get the point. So how do you form a game plan on the fly?
At this place in history in my training, 16+ months of training, I have more and more tools in my arsenal. Enough understanding that I can more than likely do most of what my Professor tells me to do as he observes from the side lines. But all this understanding must lead to the formulation of what may work and what will most likely not work on an opponent that I size up before a match.
For a smaller opponent - Use your weight and work to hold top positions, avoiding sweeps and escapes. Strength has to match up well against speed. Shutting down mobility should lead to victory.Experience is teaching me that it only takes time to figure out what works and what does not. As long as I stay on the mat and spend time on seemingly more productive routes to success, the faster I will achieve my goals. If I take a step back, eliminate all the useless stuff like emotion, appearance, and hesitation and then focus on options, the game becomes much more fun and fluid. And, of course, having Professor point out errors in judgement and style helps immensly over time.
For same size opponents - All things being equal in size, initiative must be used to stay in control of attack. Once in defensive mode, the game is much harder to play. Getting and keeping control is the path to victory.
For a larger opponent - Where is the weakness? How could you work to gas an opponent with big muscles? Is it easier to leg or foot lock a tall opponent? How can you take away their size advantage; perhaps working on getting to the back? Is it easier to choke a big guy than to arm bar?
Next time you face off against a tougher opponent, picture a better fighter than yourself, say Marcelo Garcia, and ask what would he do in the match? Then try it out.