Take a long view of the weight loss process and do not beat yourself up over small failures. The overall goal is to create a healthy lifestyle; you want to instill patterns of behavior that will keep you healthy for many years to come. In order to take this healthy view, set realistic goals for yourself, give yourself time to accomplish them, and avoid weighing yourself every day. These activities will increase your stress levels--stress damages weight loss.
By eating small portions on a regular schedule, you train your body's metabolism and avoid overloading it with huge infusions of calories all at once. People who try to limit themselves to one or two meals per day often over-eat during those meals, since they are hungry from starving themselves. Create a normal schedule for meals and follow it.