I know this is multiple pages late, but..
Eliminating as much unhealthy food from your diet (especially sugary stuff like soda, candy, etc.) as possible will make it easier to maintain a positive, confident mindset that others will be attracted to.
I hate when people say this. I hate it. This is the most inaccurate, misleading, completely baseless theory I've ever heard. Most myths have some kind of possible base under them, but this one is completely baseless. There is absolutely NO reason why consuming sugar would make you a sadder person. Depression is caused by low levels of serotonin in the brain, not high blood sugar levels. If anything, a heightened blood sugar level would improve one's mood, an abundance of food for cells leads to satisfaction, releasing serotonin in the reward pathway, increasing pleasure gained from life. The reason people claim to feel "cleansed" when eating fresher food is not because they've cleared the sugar plague from their body, it's because the influx of nutrients that were previously less available causes satisfaction.
TL;DR: Sugar doesn't make you sad