Sore Loser-Monopoly Deal Edition

When my sister came home for the weekend, I challenged her to a friendly game of Monopoly Deal. For the past year I've been pretty dominant, probably winning 15 of 20 games. But the thing is that this is the case when there are 3 or more people, so I'm able to read and predict a lot more from people's reactions. Playing with 2 people requires you to have a different set of expectations and limits you in strategic game play. Regardless, we played 4 games with my sister winning 3. My sister is really competitive, so she stated at the end that she's back to her winning ways of dominating me. Being very defensive, I pointed out that I would dominate her in 3+ player games, and that her wins were the result of lucky hands (each of her winning hands had deal breakers, just say nos, and most of the 2 card monopoly properties).

Why couldn't I just let her have her moment of winning? Why couldn't I congratulate her on her wins, and then just move on? It's not like the outcome of Monopoly Deal dictates any important decisions in my life or has any affect on how I live my life after the game. My immature response to my sister's wins revealed to me the need for me to acknowledge others' "wins" and celebrate wins with them. Another person's win does not mean I am worse off. Ridiculous. If you lose, then you lose, get better, and try again. You can't win all the time, but when you do win, let's all celebrate. This simple game of Monopoly Deal provided a means for me to once again find an area in which I needed rebuke.