So lo goes through phases of great eating and crappy eating. During his picky phases, I try not to let it bother me but I do have a certain minimum amount (certain number of bites or what not) that i'd like him to eat. If he doesn't, I get stressed out! it's something I'm working on, but it makes me more anxious than I care to admit.
For me, I guess I would want him to eat around 3-5 bites of food so he at least has something in his tummy before the next meal! (I don't give him snacks in between meals often, and if I do, they're low cal and not filling- so he'll be hungry for the next meal! In theory, at least).