I know it's senseless. I know it's unreasonable. I know it's unhealthy. There is, objectively, no reason to be in a bad mood because I lost a game being played for fun that has no stakes attached.
To be clear, this isn't directed at the person who beat me (unless it's someone who's really rubbing my face in it). I want to win, I'm doing my best to win, I wouldn't ask them to do any less, and I wouldn't get any satisfaction from a victory against someone who was pulling their punches anyway. My negative feelings are largely directed inward: when I lose, I feel like a failure even though I intellectually understand that you'd have to be a complete tool to judge anyone else so harshly for losing at a game.
I've been like this as long as I can remember. I've definitely gotten a much better handle on my emotions when I was young, but I'm sure it it still comes through, even if people don't say anything. It's not fair to the people I play with, and I wish I wasn't this way. I actually greatly prefer cooperative games over competitive games because of this, because that way if I lose, the other player(s) is/are in the same boat - we all failed together, so I can't be judged negatively in comparison to anyone.
Anyone else have similar issues? Anyone who can offer insight as to why I might feel this way?
there's this one Daigo quote I can't be arsed to dig up so I'll paraphrase: instead of focusing on winning, make continual improvement the goal. Focus on what you did better than last time, try to identify mistakes and treat learning from them as the real victory condition.
recommend reading David Sirlin's book Playing to Win to get a deeper dive into that kind of mindset and common pitfalls. The book focuses on 2D fighting games, but the lessons apply to ALL competitive games. It's free online: https://www.sirlin.net/ptw
This book should be required reading before you're allowed to play any game, IMO. Even kindergarteners shouldn't play Candyland or Tic Tac Toe until they've read it.