Good advice, from my mom. She was often referring to food choices, but this concept has great value in many areas.
We are now studying the 4th yama, which is Brahmacharya, often translated as celibacy. Literally it means “Walking with God”. So one way to approach Brahmacharya is to ask yourself if you are engaged in activities that make you feel connected to something greater than yourself. Reflect on your purpose. What lights you up? What would you spend your life energy on, if you had all the time and money you needed?
While practicing yoga, notice if you’re using more energy to maintain a pose than is needed. A balanced practice creates more energy than it uses.
Here are some beautiful musings on Brahmacharya:
http://www.yogawithamey.com/brahmacharya.html