Don't feel guilty at all. I do this (quite) regularly with dd but it only last for a few evenings at a time and then she gets the message (but forgets it again just as quickly, lol). The trick is not to give in. Oh god, I'm making myself sound like a real heartless mother - I'm not honestly - I'm just not prepared to be messed around at mealtimes when I know that she eats perfectly well, whatever is put in front of her at nursery/the childminders/grandmas house etc. When she is going through her 'good' eating phases, I will do the bribery/blackmail type thing where she is able to pick 3 things that she wants to eat (invariably sweet things, surprise surprise) eg some grapes, a satsuma, a yogurt, a biscuit, a box of raisins, a treat size bag of choccie buttons etc etc, then we divide her plate up into 3 and as she finishes each third she 'earns' one of her choices. It works to a point, but she normally only manages to earn 2 at the most, but I never give in and the ones she hasn't earnt go back in the cupboard.
I am a big believer in children knowing when they need food and when they don't and they're not stupid - they won't let themselves starve - they'll eat when they're hungry.