Competition- can’t get over losing

I work in a very competitive environment where I compete each month against another person. This person is so competitive and does EVERYTHING possible to win. (Even shady things) I am having hard time dealing with my emotions when I lose to them. This last month it was a super tight race and I lost by a very small percentage. I have been feeling so sad and depressed about this because I don’t like the fact that they wont play fair and all they care about is winning instead of working together. It just drives me nuts. I want to not care about them and just do my thing but I can’t let go of these negative emotions about the situation. I think I just needed to vent but will take any suggestions. Thx