There are some eating habits that encourage overeating.
Here are some habits to avoid:
While watching TV, online videos, etc, it is easy to mindlessly overeat food. We've all been there: without realizing it, a whole bag of chips is gone. Or a tub of popcorn or carton of ice cream. If you make eating a separate activity, you are able to focus and enjoy the food more, AND you'll eat less. (Also see Savor the Flavor)
This is, of course, called emotional eating. There's nothing wrong with eating for pleasure, but using it as "self-medication" is a sure-fire way to eat more than your body actually needs. There are other ways to relieve stress (such as exercising, music, meditation).
Today we have a lot of easy convenience foods that are unhealthy. Try to make more healthy food choices more convenient through prepackaging, precooking, etc. Also, plan your schedule so you can prepare and eat your meals without rush. (Related: The Savory Secret and Food Environment)
If you cannot seem to get bad eating habits under control, you may have to accept that you can't do it on your own. A psychologist or weight loss coach can help.
One way to help control any bad eating habit is to simply Keep a Food Journal.