I run out of energy during the day. What can I do to make sure that I can be productive throughout the entire day?

Healthy lifestyle. Make sure you have enough rest/sleep at night. Drinks enough water. Eat healthy food- more vegetable/fruits, cut down fatty food/red meat. Avoid alcohol and tobacco, exercise regularly. If you do those, you would be fine. Also to f/u with your md-for whatever significant medical problems you have like anemia, diabetes, sleep problems etc.- and have those problems taken care.