"Practicing regularly and persevering" might very well be that single most important principle.
If one can practice regularly and persevere with one's practice, one will develop strong discipline -- which is often the door which leads to spiritual growth.
From persevering, one's knowledge about the principles of tai chi will deepen, one's sensitivity and understanding of energy will deepen, and one will experience many challenges and insights. The form is simultaneously a mirror that allows us to see ourselves, and a teacher that can help us to improve.
Stressing quality over quantity in one's practice is helpful. In the long run, process is more important than product. It also helps to not allow negative inertia to get started, for if negative inertia -- or the pull toward laziness --wins regularly and settles into place one's practice and growth will be inhibited. It is best to not to skip practice, but to practice every day without fail. For once negative inertia gets started, one's energy will ceases to flow smoothly and it will become even harder to get started again. However, if one practices regularly, one's energy will remain active and vibrant and one's spirit can remain lively, which should in turn make practice fluid, interesting, and enjoyable.
Keeping one's spirit raised and with a sense of curiosity and vitalness is a key ingredient for making daily practice work.
Remember, tai chi is more the principles than simply the postures. It is the principles that make the postures and energies of tai chi what they should be. The way to achieve vitalness is to carefully and intensely study the principles. Take nothing for granted, and investigate for yourself what the principles truly mean. Though there are numerous classics and master's commentaries, one must remain vital and alive and apply one's best efforts toward understanding the principles directly and for oneself.
Stopping too soon is one of the biggest mistakes that newcomers to tai chi make. They are all too often in search of a quick fix, figuring they will do tai chi for a month or so and they will be "fixed", that they will be taken care of -- that they will have received all that tai chi has to offer at that point. They want tai chi to be an external solution which will cause some change without their participation. They expect that they won't have to take part in the process, that tai chi will do it all by itself. They don't want to be present, they just want the fix. They don't seem to get the idea that tai chi is a process that requires presence and vitality -- active cooperation in the process -- and time.
Some people stop because they just can't see the value of what tai chi is offering. They stop before catching the idea, before realizing that tai chi takes place in the "subtle" world, in the "subtle" body. Often such people refuse to accept that such an approach to awareness exists. Sometimes, even if they experience the subtle world, they cannot fathom the importance the subtle world has for affecting their life. They gloss over the subtle world with grossness and insensitivity, not realizing that the very subtlety and sensitivity they are letting go of is exactly what they need to enrich and deepen their lives.
One of the basic things that tai chi offers is beauty. It brings us together with that silent inner craving which exists in all of us -- that hunger -- to touch beauty. Whether the beauty lies in the flowing fluidity of the tai chi movements, in the sense of history, in the remarkable esthetic "look" of the postures, in the wonderful feeling of harmony, in the simplicity, in the incredible harmoniousness which tai chi evokes, in the power, or in the extraordinary feeling which its slowness and mindfulness brings, that beauty is there. It is available to any practitioner who can accept the subtle realm -- and who practices regularly and perseveres in practicing.
Practicing regularly and persevering is the principle that makes it work.