"All this happened as much as he didn’t believe in love. Well, he didn’t, right?"
The Doctor is a professor at a university in London. He was his a normal life like anyone; he has his habits; he lives his life like any other. But he doesn't get involved with anyone because he simply does not believe in relationships or any kind of feelings.
In fact he never felt any.
This until he saw Clara, and not understand how his heart beat so fast for a woman he doesn't even know her name.