Thanx for the plug, SB. But you still won't get a b-day present from ol' cheapo here...
This taanis's point is that you are denying fulfillment of satisfying your teivah to the last drop, in Honor of your Creator, in his words, "l'tzoraich Borei". You are basically recognizing that by NOT honoring yourself, by actively doing something while thinking "I do not have to satisfy my teivah", then thinking "I am doing this to Honor Hashem more than me" you are building new pathways of ingrained behaviour to break the hold your passions have on you. And because it's l'zoraich, it's NOT baal tashlich (sic intended).
I've told people who are not frum, that if they don't believe there's such a thing as a yetzer hara, they can meet him face to face. Simply sit down to your favorite meal, for me it's BBQ steak, and when you get to that last, juicy piece, put it aside and don't eat it. Don't remove it in the beginning of the meal - keep it attached to that which you're planning on eating, and then try to hold yourself back at the end. Then, tell me if you met him, and tell me what he was wearing.
They come back & tell me that not only did they met him, but he was wearing their clothes.
We have met the Enemy, and he is us!!!