I think the shy vs. distant is a good thing to look at further. They are very close to each other, and while they both create barriers to getting to know someone, shy people can still seem approachable and friendly and open to being communicted with, whereas distant seems more unwilling to engage with others and not necessarily pleasant.

The whole self-fulfilling prophecy thing is a right PITA. But if you keep people at a distance, they'll always remain distant, and then when you want to decrease the distance you'll find that they are not willing to.