How to deal with someone who constantly talks about themselves?

My dad is the exact same way. Honestly, I've just learned to accept it. He really loves to talk, so, if it makes him happy I just listen. It does get old. Maybe you should try to be more active in the conversation if it's really bothering you. Interrupt if you must, and change the subject. He will likely not even realize you've interrupted and the conversation will move in a new direction. Good luck!