I treat myself to diet soda once in awhile too, it's not the end of the world if you have some. I also have a coffee a day.
And you are right, at least that carrot wasn't a snickers bar! I steamed up a frozen veggie mix that had carrots in it last night as well, I didn't feel like picking them out and my weight wasn't affected negatively.
My suggestion is to log everythign you eat, weigh your food too. Also come join our Easter Challenge thread, there is still over a month left and you can set a small goal for yourself. We motivate and support each other to hit our goals