Zip it... Zip it good!

So, does anyone else suffer from a disease where you're completely incapable of shutting your mouth at the most inconvenient times? I do.
On a regular basis I constantly catch myself (usually during the aftermath) realizing that the situation probably could have diffused a lot sooner had I just smiled and nodded. For instance... With us buying new furniture we decided that we were not going to purchase anything that is cheaply made of plastic and particle board. So, I went on a mission to find some great pieces at a fair price. I found an antique dresser and bankers desk at well below value price. (I was practically doing jump and jacks due to self pride) The caveman comes to pick them up and what's the first thing he says? "These are not solid wood" This is where I should have just brushed it off... Nope. It then turns into a full fledge argument over how they may not be solid wood but they aren't particle board and how these pieces should not be compared to Walmart value furniture. They are timeless antique pieces that at full value blah blah blah.
Or when I get asked the same question on a regular basis, knowing the answer hasn't changed. What about the time my lamp got chipped and I should have just shrugged and said "it's ok it was an accident" instead of the 10 minute rant about the principle of the matter and how stuff should be of value to people other than myself... Yea I felt pretty dumb after that one.
Now, before you write me off as clinically insane... I know a lot of what I say could be left unsaid. Hint: that's what this blog is about! So, I have made it my mission to be better at biting my tongue and clearing my thoughts before or if I respond.
I don't know if its my patience, tolerance, or just plain irritatedness (I know it's not a word) that needs worked on but I really want to NOT be seen as such an overbearing outspoken jerk. More of a calm, reasonable, yet gets the job done kind of person.
I always INTEND on being less opinionated, less in your face my way, or just plain more passive... Yet every time someone (usually the caveman) says or does something that leads me to tend to want to smack my own head and think "did you really just ask where the milk goes" or "really?! You don't know where your own pants are?!" The filter between my brain and my mouth temporarily malfunctions.
So I'm a point where I'm considering becoming a serious yoga fantastic or possibly a woman of constant marijuana intake. (That one is a joke... Just in case you didn't know) although, people of in a constant state of high do seem to be much more passive and have an I really just don't care attitude. I wonder if they even have stress? Food for thought I guess...