I've heard this shit so much in my life. What people don't understand is that I've spent most of my life alone. I'm sick of it. I've never really had many friends or people who to spend time with, growing up. Things have improved vastly over the years. I went from being very introverted to Mr. Social.
I can be content by myself but its not enough. Over time I get bored, lonely and eventually upset. My work, hobbies and friends can only fulfill me so much. I need balance. All the balls have to in the air
IIRC, you've had a few times where you were self-sufficient. They were brief, since you've not spent much time single, however. Perhaps that's the reason: you're not comfortable alone because you've not spent a lot of your adult life that way?
PXG, I respect you, so please don't take this as me trying to say that I'm right and you're wrong about the way you, yourself, feel.