Have you been let down by people in your life? Have people said they cared but ultimately left you? I think sometimes we push people away as a defense mechanism. It hurts to lose people- so to avoid that, sometimes I think it feels safest not to get too close or rely on them to begin with.
It maybe also has to do with upbringing. My Mum died when I was very young and I've read before that motherless children as it were often grow up to be quite independent. I don't know your background and don't mean to pry but I think that can influence things too- if you had a shaky childhood.
I think it also helps to consider what it is that's annoying you. I find often people will spout a load of unrealistic platitudes if I tell them how I really am. That just annoys me because it feels like they are belittling my problems. So- I tend just to avoid the question now. Or, I just say I'm the same as always or- I'm fine if I don't know them so well.