The intermediate goals you set for yourself really matter.
Thinking of the steps to your goal as tests of your capability impedes goal attainment. Think of these steps as learning opportunities instead.
Being specific is better than being vague. The more specific you can be, the better you can monitor your performance and the results from your performance. Vague is "I'll do my best to lose weight". Specific is "The first step will be to clear away these (name them) distractions".
Don't concentrate on what to avoid and how to resist. Instead, think about what to accomplish.
Be proactive with conflicting goals like staying on a diet and going out to a restaurant. Go with a friend who is also dieting.
Plan for distractions and temptations.
Set as many intermediate goals as possible ahead of time. Goals that are already set can be initiated immediately just when you need them. Being prepared makes you more efficient in the moment. You don't have to equivocate. You don't have to stop yourself to prevent a negative outcome. You can be ready with something you want to accomplish.