I understand that this goes against any power-fantasies, but...
...in real combat? You risk injuring or killing yourself. Even with your own weapon. There's just so many variables...
You can get your finger crushed during parrying (happened to my friend during friendly sparring match because he put his finger little too forward during bind), you can slip and not only sprain your ankle but cut into your shin, you can swing and forget there's a shelf that your weapon can get stuck on if you overswing (happened to me *while practicing at home*, my wife almost killed me), you can step into a hole in the ground and fall on your own sword handle face-on, your weapon can get beat so hard it flies to your face...
...ok, maybe it's just my clumsiness
...and while I agree the 1 in 20 chance is perhaps a bit high for veteran warrior, the chance is always there. And it should be part of the game.
Unless we are talking the anime/power-fantasy "I must be invincible or I'm not gonna enjoy myself" stuff (or "it should be possible to defeat my build only by things that have level X-2 or better!"). In that case, I'm outta here