When checking out packaged food labels, look for a calories-to-sodium ratio of 1-to-1 or less (in mg). There is a surplus of salt in packaged food that affects your diet; aim for a daily intake of 1500mg. Choose foods with a 20% DV or less on anything carb, sugar, fat, or salt. We generally don't get enough calcium or protein, so don't worry about a high DV as much for them.
Omega-3 EFAs support a healthy brain, and magnesium helps you feel calm and relax. If you're feeling down, try supplements with these minerals as well as Vitamin D, as deficiencies in these areas have shown links to feelings of depression.