It took me over 40 years to figure this out. I didn't even know I was an introvert until I was about 40 and even then, 2 years later, I finally discovered my exact personality type. When I read the description of an INTJ, it described me perfectly. Just about every word that I read in this profile resonated with me. I actually thought to myself, "now here's someone who knows me!" There is nothing worse than going through life and not having anyone who truly understands you. It was so refreshing to read this for it brought about a great deal of understanding to my particular behaviors and idiosyncrasies. Basically it helped elucidate all the confusion that I have had through the years.
I used to think there was something wrong with me because I always preferred to be alone. I have always enjoyed living alone, doing activities alone. I never even got married or had any kids and I'm 44. I never had a string of friends coming and going or an address book filled to the brim with phone numbers and contacts. In fact, sometimes I wonder why I even have a cell phone other than for emergencies. I have been far more anti-social than others, but hey I love books and lectures, museums and documentaries. Put me in a room with a group of social butterflies and I was looking for the nearest exit door. This same mind set carried over into my workplace, that is wherever I was working at that particular time. I always preferred independent work because then I was more productive, efficient, and I could focus much better. Working with large groups of people was nothing but a distraction for me and more than likely would make me extremely crabby and depending upon the circumstances, very angry. Perhaps because I am very sensitive to excessive stimulus, which is typical for NT. The worse part though was when others would criticize me or make me feel as though there was something inherently wrong with me because I liked working independently or didn't go to social events. Most people would put the pressure on me to conform to what they thought I should be rather than just letting me be me. The frustration that I felt every day around most people in general just led to more reclusion. As a result though, I have read more books and have learned quite a bit. The time I have spent reading books or pursuing my hobbies rather than socializing has actually been a wonderful benefit for me.
Here are the profiles of INTJ. You can find out here and here if you are interested. Also you can take the personality test yourself and just maybe you might learn something new about your own self!