Why (and Why Not to) Castle

Earlier today I played three games a 1700-rated player. I won two games and lost one. The weird thing was that my opponent never castled. Here's game number one:

He offers me a rematch so I accept...

He offers me a rematch again. I accept it, thinking in my head, "I'm gonna win!" 

Nope.

He asked for another rematch here, but that was too much for me. All of these games were somewhat decided by castling. I hope you like my games as much as I do!