SERIOUS PRACTICEGONG, (no relation to Qigong), is a word used in China when referring to a designated amount of time that an individual sets aside daily to perform a specific activity in order to grasp a level of success, comfort & understanding of it. One hundred (100) days is the agreed standard amount of time to adequately train the mind to function within a certain behavior that in turn helps to consciously or unconsciously adjust, or mediate, the body's responses to the social & physical environment for successful assimilation into a regular activity.
This means that we pick a particular thing we want to perfect as a regular habit, (any sports-related activity, writing, singing an aria, a certain piano piece, speaking from a script, etc.), and designate them as our GONG. Then we diligently practice that every day for 100 days without fail. This means that if you miss a day, even if it's "Day 99," you start over. That alone alerts us to pay attention to our daily routine & stimulates our commitment. So when you break your routine & have to begin again, it helps you to be more aware & determined in your conscious effort to reinforce your focus.
People who manage to set goals (physical, occupational, professional, intellectual) for themselves in this manner find that this helps to reinforce developing successful patterns in their life. Dedication to anything is not merely an afterthought, but a full requirement that must be present.
Summary: In order to benefit from a beginning practice of Taiji and/or Qigong, it should be cultivated in this manner for 100 days! However, you will most likely feel the benefits before those 100 days are finished. It's subtle in the beginning, so don't think about it, just do it. The final result is that this method serves to cement these movements into your total being, and then, after the 100-day pressure is off, a daily practice of it will really do its work.
A PERSONAL NOTEUntil I found Qigong, which was 2 years after Taiji, I was an undisciplined creature. Even after I learned the basic Taiji movements, I had no direction, and certainly no instructor with a better vision of practice in general (other than to say "do it every day"), to help guide me toward a more productive & steady practice. I've always needed some sort of RITUAL to follow that helps me to embrace something I really need to do…that's just the way I roll. Until a Qigong master explained that I needed to follow an organized path with a set goal if I was to ever be cool with any of it, a daily practice of anything was an alien concept. He was right, and then explained GONG, and so I began my journey! I started with 100 days of Qigong; then 100 days of Taiji. This helped to validate it correctly into my life.