Correction: Once you lose self-control you're screwed.
However it doesn't matter how much self-control you have if your understanding of proper nutrition or your access to healthy foods is limited. Unfortunately this is often the case and most people struggling with weight management are not even aware of it. It's not their fault! We aren't taught what things in school like the difference between simple sugars and complex carbohydrates. (1) There's more to a nutrition label than just fat and calories. (2) The majority of foods that are most accessible are NOT optimal for weight management.
Managing one's weight requires an understanding of nutrition and how the foods we eat affect our body, then using that knowledge to make good choices (self-control) about what to eat.
Yes it's a challenge. Mother nature and the foods most of us were raised on are not kind in the long run. You're only screwed if you deny personal responsibility and fail to realize how much control you have over it, or, how much control it has over you.
Research, experiment, gain an understanding of the issue. Have some faith in yourself and keep working toward that realization.