Maybe I should have tried to stop myself from finishing the thought once I realized its nature? Or you just have to pay even more attention, and it will come with practice?
I don't think you should simply try to stop yourself. I think you should apply the insights of cognitive behavioral therapy. Talk to yourself about it, and you might find that you were reacting defensively because you believed on some level that losing the argument would be a terrible event. (Or perhaps you were otherwise motivated; but the important thing is that you were motivated, as the title of the post indicates, and you should try to find the motivation.)
CBT would then recommend that you build a habit of reminding yourself that losing arguments might be unpleasant, but it isn't the end of the world. CBT theory predicts that eventually you'll change your thought pattern and become less averse to losing arguments. That should result in being less defensive and more objective.
Then post the results!--either as a warning or a celebration.
Good advice, I will look into it!
Yesterday I caught myself on rationalizing. It's the first time I caught myself on rationalizing before I finished (verbalizing) the thought. But, I finished the thought, and even though I knew it was rationalizing from the very start, I ended up believing it.
The original question is not very interesting, but here it is to illustrate the issue: I was talking with a friend about US TV series. And he mentioned that his wife insist on watching movies/shows in English without subtitles; to improve their English skills. (I also started watching American shows many-many years ago with the purpose of improving language skills. In English with English subtitles. And it did help immensely, but I never got rid of the subtitles even though originally I was planning to.)
So, my though answer was the following: "How does she know that this helps more than watching with subtitles? Did she measure it somehow? Watching without subtitles mainly helps with listening comprehension. And I'm already good enough with that. Using subtitles on the other hand is always an opportunity to improve on the more obscure part of English vocabulary. In almost every episode there is one or two very rarely used words, English vocabulary is just so enormous, and without subtitles you'd just skip over it..." Fully verbalized it was something like this.
Now, the first part of that argument is a "fully general counterargument". And the rest of it, though might be plausible, should be treated with great suspicion since I know that the roots for it are in motivated skepticism. At least, my realization that this is rationalization stopped me from using this argument. But, it is still quite hard to "unbelieve" it. Maybe I should have tried to stop myself from finishing the thought once I realized its nature? Or you just have to pay even more attention, and it will come with practice? Of course, this is a trivial issue, completely unimportant. But why would I think that it will be easier if the issue is important?