Most people are sociable. If you are extremely introverted and overly fond of being alone I think that can lead to mental illnesses like social phobia.

well, i dont think being sociable is a good choice.but sometimes we cant choose. on some occations we must be sociable though we dont want to be. being sociable is really tiring. To a great extent,what we call "mature" usually means sociable. but i think what most important is being yourself. YOU ARE WHO YOU ARE. and no one in the world could replace you. sometimes it is really depressing when we cant choose to be naiev. just being what you like .and stay happy that is the most important thin and good luck to you. if you wanna know more about this, you can read the books by Nietzche. i think Nietzche's books will do good to you.