Sorry to learn about your difficulties. Low mood as a reaction to life stresses and disappointments is common, but if you built up your coping mechanisms you would be able to handle them better and still focus on your long term goals.Adequate fluid intake and good balanced diet, without missing any meals and taking care of all nutrients would help.
A good night sleep is very vital, but if you are working in nights adequate sleep with adjustment of biological clock is important.
Mental exercise, physical exercise and creative hobby are equally important, but need consistency with this.
Having a network of family and friends and spending quality time would help too.
After trying above consistently for a fortnight, if you still feels problem is not improving, consider seeking psychological counselling for the same.