A healthy, balanced diet, with moderate caloric intake is a major factor in how you feel day-to-day, and in your longevity. As a rule, eat plenty of vegetables and fruits, whole grains and beans, fish two or three times a week, low-fat dairy and meat, and minimize white flour, sugar, and alcohol.
To optimize mood I recommend a good quality multivitamin, vitamin D (dose depending on blood level), fish oil with EPA > 500 mg., and methylfolate 7-15 mg. (after testing for MTHFR gene type).
About 100 minutes of cardiovascular work per week is good. This can be as simple as fast walking, or choose activities that are fun for you. 30 minutes of getting your heart rate to 60-80% of your maximum (220 minus your age), six out of seven days per week, can be an effective treatment for depression, as good as an antidepressant.