Being overconfident and having unrealistic optimism often spell the d-e m-i-s-e of the effort to lose excess weight.
Why?
Overconfidence is a shield for those who would score low if there were an inventory of skills for losing extra weight. Unrealistic optimism is yet another self-esteem protector. There are two forces that could be at work here. One probably is a lack of skill, and the other could be a lack of awareness that the skill level is sub-par for the weight-loss process.
A good solution: develop the skill it takes if you want to lose weight.