Teach a technique and if you’ve got students who are curious (and let’s hope you do) then they’ll ask: “but what if they…” Yes. What if they do that? What would you do? Try it and you will see. If it works it was a good variation – if it doesn’t, then it wasn’t.
Often times a partner reacts in a particular way that makes the technique you’re working on completely inapplicable. In such a case, don’t force it. Don’t be the person who tries to hammer in a screw or even worse, screw in a nail. Switch tools.
In the beginning, it will be difficult to know what tool to switch to. You may be working on how to defend against a straight jab and your partner throws a hook. Yikes! What should you do? You should defend against the hook. How? Hopefully by doing something that stops you from getting hit.
Over time, you’ll drill enough specific techniques and get enough sparring time in that defenses, counters and ways to adapt to changing martial circumstances come naturally. Training the “what ifs” will help this magic moment arrive sooner – because when that “what if” comes up again, you’ll already have an answer.