You wouldn’t expect your car to run on empty so please don’t expect your body to do so either. You don’t have to go on an extreme diet to improve your mood, just try to eat a little better. Small manageable habits are better changes in the long run. Eat regularly, and eat healthily. Have a look at this section if you need some nutritious and manageable recipe ideas. They’re written by working people and not Michelin starred chefs, so you won’t need any truffle oil, but you will need fresh veg and a bit of willing.