What, according to you, does Aristotle mean by "pleasure proper to tragedy"?

In Aristotle's Poetics, he
says:

Those
who employ spectacular means to create a sense not of the terrible but only of the
monstrous, are strangers to the purpose of Tragedy; for we must not demand of Tragedy
any and every kind of pleasure, but only that which is proper to it. And since the
pleasure which the poet should afford is that which comes from pity and fear through
imitation, it is evident that this quality must be impressed upon
the incidents.

This is found
in Aristotle's first and most important "principle" of tragedy: plot.  A viewer of a
tragic play will, by the end, feel an aesthetic (artistic appreciation) pleasure in the
intricate plot which elicits a catharsis, a purgation of pity and
fear.

For example, by the end of Oedipus
Rex, we feel an appreciation for all the tragic ironies involving sight and
blindness, fate and free will, family love and incest, and truth and ignorance.  All of
these feelings are the result of a complex plot, a series of oracles, ironies, and
complications that, it seems, were destined for tragedy.  Ironically, we enjoy the facts
that Clytemnestra kills herself but Oedipus doesn't: it seems just to us.  We pity both
mother and son, and we fear that such corruption may befall our families as well.  So,
the pleasure comes at intersection of pity, fear, and appreciation of a plot that is
resolved tragically but deservedly.