No matter how long you know someone, or how much you've read their blog, you never really know everything about them. You don't know about what they're thinking all the time, you don't know how their mind works at all. You can't possibly know anything about their relationships, because you'll never know what goes on behind closed doors.
People don't know everything about me. They don't know that I can be so passive that I avoid confrontation at all costs. Most people don't know I cry over dumb things, like Steve Carell's last episode of The Office. Seriously though, if he hadn't said goodbye to Pam I would've been so mad. People don't know that my feelings are easily hurt, because I don't say anything.
I don't claim to know everything either. I don't understand people at all sometimes. We were pretty confused about our loud neighbors. Why were they being so loud in the middle of the night? What could they possibly be doing at 1 am, that would consistently make loud noises, and bang against the wall, until 7 am, keeping us all awake? That's why we called the cops, and when that didn't stop the noise, called the landlord the next day to complain. There's no possible way we could've known that the cause of the noise was one of the tenant's nine year old son, who is autistic. If they had explained that prior to the noise, or even after, we would've been more understanding. We could've compromised, and possibly told them just to go into the front bedroom, that doesn't share a wall with our bedroom. No cops or complaining necessary.
No one will ever understand me or the way my mind works, but I'm nowhere close to understanding them.