When I first started practicing Kundalini Yoga, I heard of a practice within the tradition to keep the hair uncut. I had always wanted to grow my hair out so I thought, why not. It grew long and luscious as my diet nourished my body and the protein in my diet helped my hair grow quickly. In December of last year, I decided to cut it and took 6 inches off. It amazed me how different I felt. In the past, I would have loved the feeling of a fresh chop. Suddenly, I felt very insecure, very childlike, and as if I lost a lot of my sensual energy. I have not cut it since, aside from my bangs, but cutting them short enough to not cover the space between the eyebrows where the pineal gland resides.
"The bones in the forehead are porous and function to transmit light to the pineal gland, which affects brain activity, as well as thyroid and sexual hormones. Cutting bangs which cover the forehead impedes this process. When Genghis Khan conquered China, he considered the Chinese to be a very wise, intelligent people who would not allow themselves to be subjugated. He therefore required all women in the country to cut their hair and wear bangs, because he knew this would serve to keep them timid and more easily controlled." - Deva Kaur Khalsa
I learned my lesson. It's definitely not a practice for everyone but it was within breaking the 'rules' (only they're not really rules, you can do whatever the F you want) I learned about it through experience versus just doing something because someone said to do so. It became even more fascinating to me to learn how much power something so seemingly simple as body hair holds and how we don't even realize that power we hold.
“When the hair on your head is allowed to attain its full, mature length, then phosphorous, calcium, and vitamin D are all produced, and enter the lymphatic fluid, and eventually the spinal fluid through the two ducts on the top of the brain. This ionic change creates more efficient memory and leads to greater physical energy, improved stamina, and patience.” - Yogi Bhajan
More info on the Yogic Science of Hair Care here