"If you have to make a show of it, you haven't got it...  Right?"
          -Mairsil, wizard in training 

More on the Hazards of using Magic:

   Many non-magic-users believe that the excessive usage of wizardly
magic will drive the practitioner insane.  This is not so.
   Well, mostly.
   At least, not entirely.
   Wizards aren't entirely clear on what it is: whether the lust for
power causes the most elite of their kind to deliberately alter their
thought patterns, or whether the power itself has some sort of
corroding influence.  Few have dared to ask, and those who have, haven't
learned anything productive.  Most wizards' logical and deductive
abilities remain sound; they remain coherent in conversation; their
memories are fine, which is startling when you consider the amount of
magic that pours through them.  It's just that they develop...
   Poor taste.  That's the best way to describe it.  One day, almost
out of the blue, it seems, they'll start walking around town in pointy
hats and colored robes, often with long, flowing white beards, false
wrinkles, and gnarled staves.  They start using phrases like "Gadzooks!"
and "Hark!".  Some build huge, fancy castles for themselves; others
adopt names like "Stormcrow" or "Bandit Slayer" or "Blue Rider" and
wander through the wilderness.  Few - and this is the truly odd thing -
very few of them have been observed to actually use any magic, except
in direst need; but those that do are always amazingly strong.
   Black mages usually get it the worst, with artificially white skin
and glowing eyes, levitating an inch off the floor, the whole bit.
White and blue mages are almost as bad, though, to be honest, with many
blues it's not much of a change from what they usually do.  Green
wizards usually go off and live as hermits in the forest, and red...
Hmmm...  Actually, nobody that you ask has ever seen or heard of an
old pure-Red mage.
   The theory has been proposed, thousands of times among as many
apprentices, that, perhaps, the image this creates in people's minds,
particularly the mind of the wizard himself, somehow augments his power;
but that these "style reserves", once drawn upon, are depleted much more
quickly, and replenished more slowly, than normal magical energy.  Only
the wizards themselves know for sure, though, and they aren't telling...