In macrobiotic we talk about yin and yang principle a lot.
Yin is an expanding energy and yang is more concentrated, contracting energy. like everything else some foods are more yin than others or vice versa. nothing can be purely yin or yang but can be seen as containing more or less of each quality, compare to other foods.
For example meat is considered to be very yang and refined sugar is considered to be very yin. The goal is to find ourselves balanced physically, mentally and emotionally between these two states as having too much of either yin or yang energy can throw our physiology and mentality out of balance.
The effects of each food will be different for different people as well. A person who is normally more yang might have a piece of cake and might not feel the imbalance after, while someone with more yin quality may.
You may decide to eat accordingly in order to achieve a specific emotional state. If you feel that you are feeling more stressed, and aggressive you may decided to include something more yin in your next meal. (I am not suggesting here to eat white sugar loaded ice cream here! because it is so extreme that throws you right out of balance, bring the feeling of inactiveness, depressed and spaced-out feeling) It might be more leafy vegetables, fruits or desserts that are made of quality sweeteners, such as rice syrup, amazake or maple syrup
this principle can be quite complicated more mysterious as you go deeper into the philosophy but they are very interesting.
How yin attracts yang and yang attracts yin (yin oxygen attracts yang hydrogen making water, Yang boys and yin girls)
On the other hand we may make choices that violate the actual force. (yin repels yin and yang repels yang). Like trying to put minus and minus together on magnets. too much alcohol (extreme yin), staying with a job that crush you day after day. We deny ourselves our attractions because we will be enslaved by the temptation. That will cause some unhappiness in your life.
It is important to stop to see how you are feeling and your body is feeling. When it's time to let go of something let it go. let the universe or natural force (or whatever you'd like to call it) do their thing you will feel happier and more balanced.
(I know I'm not perfect. it is hard sometimes....)