It's somewhat annoying, but very true: controlling portion size is really key. Anything in excess is excessive, no matter if it's whole wheat pasta, apples, carrots, or chocolate.
WebMD has some fabulous guides to help. Here's a Link to the full resource: http://www.webmd.com/diet/healthtool-portion-size-plate - and they have a one-pager that you can post on your fridge or keep on your computer or phone.
The website ALSO has some really great VISUAL examples of correct portions by food group, here are some of my faves.
Images here are (c) WebMD.