I find Tann's comment interesting, specifically the bit about introverts having a "higher resting level..." Psyching up before a session or lift leaves me burned out shortly after a few warm ups or only a single heavy attempt. I'm extremely introverted...
I do prefer to lift alone.
Training is simple/abbreviated.
Low reps at higher intensities.
Clear mind, no psych up.
I like loud music but no interruptions. I think I use the loud music to drown out my own thoughts more than anything.
Need my alone time and often a lot of it (drives, walks, long shits, etc)
Not a fan of crowds.
Sociable, friendly, but somewhat shy... no problems with a handful of people, but beyond that I usually keep quiet.