I would rule against it. If it were that easy to kill yourself, then any feature on a sword would be equally harmful to the subject. The cool thing about magical items is that it is willed by the wielder: once it is unwielded, its magical properties become inert, thus negating the magical property. That is why a firebrand +1 will not burn inside its sheath. If a natural one causes the character to lose grip of the weapon, the magic should automatically deactivate, accept for obvious reasons that makes the magic still active when it is unwielded, like a returning dagger +1. There is a reason why mages need high intelligence and to study often.
Heck, in the case of psionics the various psion disciplines were all keyed off different abilities, including strength, dexterity, and constitution. From all I've read about it, it was actually fairly balanced that way.
enemies can't fumble, and yet again, a 6th level fighter now fumbles twice as often as a 1st level fighter? Even worse for twf'ers. Stupid needless nerf to weapon users.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.