It's unrealistic to think that we'll ever only eat "good" snacks. Though it's best to stay away from processed sugar and foods, any snack is "good" if eaten in moderation.
Realistically, snacks shouldn't consume more than 5% of your daily caloric intake.
2,000 calories x 5% = 100 calories.
A cupcake? How about a half of a cupcake?
A bowl of ice-cream? How about a small cup.
Much of our problem is the container that we eat our snacks from. Large bags, plates, bowls, spoons make our already large portions seem not that large.
Be the Little Bear.
Art courtesy of: http://www.elfwood.com/art/k/r/kristenste/goldilocks.jpg.html
