An interesting excerpt from the "Life and teachings of two immortals v.2" by Hua Ching Ni:

Use the strength of your study and mental energy to plant an inner willingness to be open to internal teachings that will keep you moving in the correct direction to maximize present or future growth.
Wisdom, mental clarity and spiritual purity are needed in every age of your life. Nobody can be excused from not becoming improved internally, spiritually, mentally and emotionally.
And about not neglecting the external vs. internal (a mistake made by so many adepts) - I also believe that there must be balance, as without balance there is always a disturbance and the way is distorted:
For both men and women, spiritual practice is of tremendous importance. The internal spiritual energy cultivation will make their beauty and life enduring and maintain their youthful look. Although looking good is an external thing, if you give up your external things, what is your internal reality? Both are important.
And about the balance itself (I already wrote somewhere about 5 energies - or 5 elements / wu-xing in the taoism):

When five types of energy are in harmonious order within a human being, tiny, invisible but real spirits are produced. These spirits join and strengthen the being. When the five types of energy are in disharmonious order within a human being, disaster will occur.
One who discovers the spirits and understands their functions in life will thrive and become prosperous, healthy, self-sufficient and have better opportunities, etc. The same five energies are in the minds of people; when a person sets them in action in a harmonious way, all spirits are at his disposal and do his bidding, and all things receive benefit from this person.