The Greeks elaborated tragedy out of the Dionysia, yearly festivals of sexual abandon. Yet their central theme and pre-occupation was the realization that we can never know for sure the results of our choices and actions but must nevertheless choose and act. We can never know for sure the right path to take nor once chosen can we be sure we have avoided the wrong path. We can never be sure what the gods have in store for us. Sometimes, we must chose between alternatives both with equal claim on us but also mutually exclusive. Often we must choose between alternatives mixing the good and the bad. And yet we must choose.
The tragic flaw is that in our character, in our pattern of being, which leads us to err, to choose, in a way that we and others may be able to predict but which we are powerless to avoid. Confronted by choice and even knowing the good, we choose through emotion, our reason overcome, and in a way that lends a special sense of doom to our actions.
Bad choices are bad choices and often tragic in their outcome. Tragic in that they force good people into situations where their choices are between actions equally bad. Witness Bush's decision to invade Iraq with the many compromising choices it forced on the millions of people affected by that decision.
Tragedy lies in those occasions where their are no completely good choices but we must nevertheless act, when even inaction would be a choice. To create tragic situations is evil, as the Greeks came to understand of their gods.