Characters Control Me More Than I Control Them

It's amazing how when I plan out a character on my pre-planning Word document, I have them setup a certain way, with certain flaws, and a specific personality. They generally start out the way I have them planned, but they almost always inevitably end up changing wildly and going in some new direction that I had never planned. It generally works out when this does happen, but it always catches me by surprise.

Granted, the character never completely careens off course and ends up turning from p...