What you eat and drink can dramatically affect your energy levels and biochemical composition, which in turn affects your emotional and mental clarity. There is simply not enough energy to think clearly or initiate and sustain the changes needed for us to take good care of ourselves when our diet is deficient.
However, you are not what you eat, you are what you absorb!
Based on my own experience, I recommend eating a varying diet, using only "real" food and making it as simple as possible so that it is practical and ideal for everyday life, eating five times a day and always eating as much as you need. As for drinks, nothing can replace pure water; tea, juice, or beer are not replacements! Don't buy juice, it's just sweetened water! Make your own juice instead, or even better, eat the fruit as it is.
When you eat optimally, you will function optimally!