Food; it is fuel for the body and one of the biggest sources of stress and enjoyment in our daily lives.
However to really see some results with your training you need to be fueling yourself with the right food and taking in the proper amount for your goals. To down play the impact your diet has on your training would be a huge mistake. You are what you eat! Meaning the food you consume is the building blocks for your next layer of skin, your organs, your muscles.
How do you know what foods to eat and how much? One way (and it is a very personalized way) to get a better idea of what works for you is a Food Journal. Write down what you ate, when you ate it and how much of it you consumed. On top of that you can write a general description of how you felt that day. After awhile you will start to notice patterns. The food that gave you energy, the foods that made you feel tired. Furthermore, I have found that a lot of people think they eat well. Then they look at their food journal and realize it needs a little adjustment.
Keep track of your food and you will find yourself feeling a lot better with more energy.