This post, I want to talk about endurance in argument. Like physical martial arts, rhetorical combat can be tiring in its own way; it takes a lot of mental and emotional effort to do well, and the longer an argument goes on, the more tiring (and tiresome) it gets. Again, as with the physical martial arts, proper technique can help a lot, because it helps you to apply your effort more efficiently. As well, knowing proper technique reduces stress, which is itself very tiring.
But there is another trick to improving your staying power, and that is to frame your goal differently.
Many people go into a debate with the objective of convincing their opponent, which makes a certain amount of sense. After all, that's what all of your arguments are (or should be) built for: to be as persuasive as possible in supporting your claim. So it's natural to say to yourself, "I'm going to keep arguing until I win! As soon as I convince my opponent, I'll be done!"
This is a fine objective, but the problem is that however confident you may be that you're right, your opponent wouldn't be arguing if she didn't feel just as certain she's right. And she's probably made up her mind to keep on arguing until she convinces you. Neither one of you considers defeat an option; victory or nothing! And you can't both win on those terms.
Now, while determination to succeed is certainly a good thing, it's a bit of a trap in this case. If you're determined to fight until you win, and your opponent is anywhere near as determined as you are, eventually one of you will become so exasperated at the other's unwillingness to see reason that they'll conclude victory is impossible, and give up. Not concede defeat, mind you; they'll just say something like "It's pointless arguing with you!" and storm off.
The person who gives up first is often perceive to have lost, at least in the contest of wills, which is why they so often try to frame their retreat in face-saving terms that blame the opponent for being so unreasonable. It may or may not be an actual victory for the person who stays, but it is at least an advantage in the eyes of most audiences.
The point here is that if you set out planning to argue until you win, you've got maybe a 50/50 chance of being the one who gets frustrated and gives up first, regardless of how right you are. Indeed, the more certain you are of your position and the obvious wrongness of your opponent, the likelier you are to conclude that their refusal to see reason is due to wanton stubbornness, rather than genuine good-faith disagreement.
So do not set out to argue until you win. Instead, set out to argue until you lose. That is, decide that you will continue to defend your position until you are persuaded that it is no longer defensible, and you are forced to change your mind.
I have found this approach to be very helpful in allowing me to keep up my patience in an argument, because it is no longer my failure to persuade my opponent that is prolonging things, but my opponent's failure to persuade me. That alone significantly reduces the mental stress and emotional fatigue of debate, but there is another significant advantage to framing the goal this way: it is the proper stance to take to effectively apply the Socratic method.
If my goal is to be convinced, rather than to convince, I will take pains to help my opponent express her position as clearly as possible, so that I may better understand it. And to that end, I will try to make my objections as clear as possible, in order to help my opponent (who may have already faced and overcome these same objections) put them to rest.
Some people will think there is a danger to this approach, in that you might actually end up losing the argument, and being convinced by your opponent. I don't actually consider this losing, because you end up with a better understanding than you had before, but even if it is a defeat, this is another respect in which rhetoric is a martial art: a win is empty without the real possibility of defeat, and there is much to be respected in the warrior who acknowledges having been honourably beaten.