Let your wife win once in a while.
My wife and I love board games. Right now our favorites are Ticket to Ride, Quarkle, and Stratego. However I am really good at strategy games and I tend to win. This often makes m wife not want to play with me because she hates losing.
I am extremely competitive, and I have a hard time turning that off even when I am playing against my wife. If I don't learn to stop she will not play with me anymore