I'm an introvert, with a fairly small social circle. In fact, I was just having a conversation with someone about how Facebook does or does not reflect how we implement interpersonal relationships in our day-to-day lives, and I mentioned that I looked at the number of "friends" I had on Facebook a couple of months ago and promptly dropped about 2/3 of them, because it was improbable to me that I had that many people I would call "friend".
I have no bitterness over the notion that people with extensive social networks may live longer than me. I'm fine with that. IN fact, it just gives me more motivation to live the life that I want and that makes me happy while I can. And if that life means more time reading a book on the couch, or riding around on the back of my bike by myself...I'm totally fine with that, because it's what keeps me happy. To be honest, I've never really thought I'd make it past about 52 anyway. No, I don't have a death wish, it's just a number that stuck in my head when I was pretty young. So, in my brain, anything past that is just bonus time. 
As far as Meyers-Briggs goes, I'm an INTJ. If you read the description of an INTJ, it's definitely reflective of the core of my personality...and certainly in my professional life.
For anyone who is familiar with the Enneagram, I'm a 5. That's something that's also pretty descriptive me, but it goes a little deeper than the Meyers-Briggs, with more variation in personality and motivation drivers.
2009 BMC Road Racer SL 01 / Specialized Ruby 155
2007 LeMond Reno / Luna Chix Team Saddle
1980-something Lotus Odyssey / Brooks Finesse
1992 Bridgestone RB-2 / Brooks B-17 Imperial
Nada Bike singlespeed / Brooks Team Pro in white