Resist or yield
Dieter: (starting off in discussion mode, possibly this will turn into a stable page)
It occurred to me that a distinguishing aspect of good play is knowing when to resist and when to yield. Strong players have fighting spirit: they do not want to obey their opponent and give him everything he wants. On the other hand, always resisting is bad. If you do not yield from time to time and give your opponent something, your forces will be scattered and overstretched. A fight which takes place in the opponent's sphere of influence may not call for fighting spirit or it becomes all deciding and likely at your detriment.
Yielding wherever the opponent makes a claim is also a certain way to defeat, albeit a slower one. You will be pushed around?, end in gote, lose stones and let invasions live easily in your moyo. Stated this way, knowing when to yield and when to put up a fight amounts to playing well. So how do we decide?
A first concept that seems useful to me is forcing. If your opponent is forcing you to do something, it feels bad. And when you can force your opponent to do something, it feels good. So if you can yield superficially, while forcing the opponent to carry out his claim, yielding may be positive. But that moves the hot potato to the definition of feeling to be forced.
A second mental device to know whether to resist, is to inspect the opponent's claim. Does it claim to get a major strategic advantage? Or does it merely claim to take a few points? If the claim is "I will catch these stones if you do not respond" then it is worth while investigating the line where you force your opponent to take the stones. If this looks good, then these stones are probably disposable stones. If they are cutting stones forcing to take them is usually a big gift to your opponent.
If the claim is, I will penetrate your sphere of influence, this may not be something to resist either. You should probably welcome your opponent to put stones where they are unlikely to live. What you want to resist, is that the sphere is easily dealt with (reduced).
This leads to a third mental device, and probably the easiest to apply. In your own sphere of influence, you are not willing to make many compromises. This is your sphere of influence and you should get the maximum out of it, not necessarily in terms of territory, but in a broad sense. In your opponent's sphere of influence on the contrary, you are ready to accept most compromises. Achieving something where the enemy is strong, is positive, however small it may look.
examples and diagrams to be added; I'll add some
Aspects of resistance are:
Aspects of yielding are:
Bob McGuigan: Consider a fairly common maneuver: I have a moyo, my opponent invades, I let her live under pressure and build/transfer my influence elsewhere. Is that yielding? resisting? It could be yielding in the manner of "You want that? OK, take it, and I'll take this instead" Or it could be resisting in a martial arts sense of turning the opponent's attack against him. One of the striking things I notice in professional play is how often defensive plays also have some offensive character. For example, Black tries to take the base from some white stones and White defends but in a way that weakens some nearby black stones. White yielded (defensive move) but at the same time resisted (offensive potential).
unkx80: Resisting versus yielding is not always that clear-cut. Play kikashi before defending is a prime example of resisting a bit to obtain some profit before finally yielding. On the other hand, such struggles can lead to exchange and mutual damage when both players don't yield. By the way, I think that sacrifice is not necessarily yielding. Yes, you give up something, but often in return for something else.
tapir: For me this relates almost exclusively to (moves meant as) kikashi all other cases are not so clear. My impression is weak players yield out of habit, stronger players resist out of habit, even stronger players end up yielding more often again - because their opponents moves are indeed forcing. On my level I feel resisting is actually a bad habit.