"Do not go lightly to the written page."
King's first rule. One I've tried to live by.
I broke that rule today, yesterday, and the day before. I got embroiled in a discussion of trade publishing vs. self-publishing with an author who has decades of experience on me. I did not argue well. I did not take percieved defeat well. I went hastily to the written page, forgetting that a web forum is also a page. 
I felt cornered and criticized and stubbornly hung on, because I was emotionally invested, and as such I alienated an elder writer and rendered any point I may have had moot. I tried to keep things civil despite my mounting frustration, and failed. 
Assessing the fallout... not horrible, but not good. I wasn't banned, so I'll have a chance to try and amend my behavior on those forums going ahead, but it's definitely going to color interactions with the other forumites for a while to come.
It may cost me some professional opportunities in years to come. See, that's the downside to the internet, when you're making a living with your name attached to your reputation and work. If you screw up and act like a jerk, then those words are there decades down the road. Worse, if you act like a jerk in a niche community, then OOOOoooooohhhhh they'll remember that.
:: Sighs :: I may get a little leeway for being relatively new and ignorant. We'll see. 
Time to build up thicker skin, prioritize acting professionally, avoiding arguments, and being as pleasant as possible to everyone. 
I'm beginning to see why so many writers drink.