who maintain the Tao do not want to be full

"Chapter 15

In ancient times, those who were well educated were in communion with heaven, and were subtle, profound, mysterious and penetratingly wise.
Their depth was unfathomable.
Because of this, they appeared reluctant, hesitant, like one wading across a stream in winter;
Wary, as if there were dangers on all four sides;
Solemn, as if a guest;
Yielding, like ice on the verge of melting;
Pure, like uncarved wood;
Broad and expansive, like a valley;
Chaotic, like muddy water.

Who can still muddy water and gradually make it become clear?
Who can make the still gradually become alive through activity?
Those who maintain the Tao do not want to be full.
Just because they are not full they can avoid wearing out and being replaced. "

from
http://www.terebess.hu/english/tao/tamgibbs.html

written published sources

The five main written published sources in the last nine years are in the order I read them over about that time span are:

1 Tai Chi by Paul Tucker, Lorenz Books, ISBN 1-85967-503-4
2 Principles of Tai Chi by Paul Brecher, Thorsons, ISBN 0-7225-3474-4
3 T'ai-Chi, The "Supreme Ultimate" Exercise for Health, Sport, and Self-Defense by Cheng Man-ch'ing and Robert W. Smith, Tuttle & Co., ISBN 0-8048-0560-1
4 The Tai Chi Book by Robert Chuckrow, YMAA Publication Center, ISBN 1-88696-64-7
5 T'ai Chi Ch'uan Ta Wen by Chen Wei-Ming, North Atlantic Books, ISBN 0-938190-67-9

They all helped me at the stage I first read them, the last three in particular are still referred to regularly.

Need for Homework

You have to understand a field well before you develop a good nose for what needs fixing. You have to do your homework. See this article