We've been discussing this in WW Ann. Some of the suggestions were:
Don't sit at the table if your meal is done. Get up, scrape the dishes into the trash/disposal right away.
Immediately get the utensils in the sink. If you're soaking a dish put them in there.
If there's a Tbls. of this and a 1/4 cup of that left toss them. Just because there is not enough to save doesn't mean you have to eat them. If worst comes to worst pour something on them before you leave the table. Nothing like diet coke over spaghetti to make you put it in the trash.
If you've got a skinny dog (I do) let it have the leftovers.
Throwing away bits and bites is not a sin. If you eat them, and especially if you eat them and don't count them, you'll be carrying them forever as penance.