Ten got *very* messed up in the head, it has to be said. He tried to be so many different things that he wasn't meant to be that he didn't know what he was anymore, and he was constantly seeking approval from his companions, (i.e. "Look at me! Look at me!") And then, by the time he's Eleven, he suddenly knows who he is: Gandalf. Sort of a Space Gandalf. Or the little green guy from Star Wars. Woooom!

One thing I always thought was interesting was the fact that Ten seemed okay with dying on many occasions. In fact, during The Next Doctor, he seemed rather fascinated by his 'future' incarnation, and seemed rather hopeful for some banter, (i.e. "Not as young as you were when you were me!")

~ srmcd1