I hate losing. Particularly when the gap in skill level between me and my opponent is really wide. I don't see any point in playing when the odds are stacked against me from the get-go. Yes, I know I won't learn to play better without getting beaten by other players, but I fail to see how getting hammered into the corner and dying because I couldn't react in time teaches me anything at all.
Compounding this problem is my poor execution, half the crap I want to do not coming out thanks to lag (network or input, take your pick) or the emulator turning my stand C into a C throw even though I had let up on the arrow keys a full second ago.
Maybe I just don't have the mindset for games like this.