"I wish I hadn't eaten that piece of cake. I realize now that I'm smart enough to make better desicions. I only hate because I was stressed out and I needed something to calm me down. This mistake was just part of my learning experience to lose 10 pounds."

This kind of talk will give you more motivation and it will not make you feel bitter about your actions. You can change your self-talk with awareness and practise. Below are some examples of negative talk, joined with positive alternatives:

Focusing only on the problems: We dwell on the problem, instead of the solution. Instead: Assume that most problems have a solution, and ask "How could I make this situation better?"

Expecting the Worse: "What if I gain 20 pounds?" "What if he doesn't like me?". Expecting the worse does not incourage you to reach anything. It only promotes anxiety. Instead, ask yourself a more positive thinking outcome. "What can I do to prevent myself from gaining 20 pounds?" "How can I make a good impresssion?"

Thinking in Absolutes: We exaggerate reality with words like "always," "never,"
and "everyone". "I will never be slim--I always eat too much." Instead: Replace the exaggerationg with more accurate words. "I often eat more than I need, but I can change that."