Dark chocolate will be helping because of the theobromine, an addictive compound that is related to caffeine that also stimulates pleasure receptors in the brain (it actually breaks down into the same metabolites as marijuana). Truth is, theobromine is actually a poison. Nobody likes to talk about chocolate being poisonous, but it is. However people rarely eat enough of it to experience theobroma poisoning but it does happen and its an addictive substance too. Generally speaking I try to limit chocolate and counsel people away from consuming anything containing addictive compounds.

As for stress, there have been studies that have shown that people with higher fruit consumption generally experience more stable moods. Keeping very well hydrated is also very important, as is exercise and good sleep. Not only good sleep, but habitual sleep patterns.

Valerian is a herb that can help with stress but it also can make a person feel drowsy, which is why most take it shortly before sleep. Lavender also helps with stress (aromatherapy). Hawthorn tea can also help.

I don't follow the reasoning behind eating more salt to alleviate stress. Not only does sodium cause water retention it also elevates blood pressure. I would avoid anything with salt, personally.