Remember your goal. Challenge the logic behind this kind of erroneous thinking. Dispute the notion that self-worth can be measured in terms of body fat. Of course this makes little sense. If you stop berating yourself, you'll reduce your anxiety, depression, and self-loathing, and thus may find it easier to manage your weight.
Many people try to lose weight for years with little success.
Some people accept this struggle without upsetting themselves. A lot has to do with their thinking. If you fall into the second group, stop for a moment right now and get in touch with your dysfunctional thinking. If not, I'm worthless. This kind of thinking plagues many individuals who continuously fail to reach their idealized body weight.