The conventional wisdom is: you are doing it too fast or eagerly. True sometimes this is the problem. But then doing it too slowly in internal disciplines will never get you THERE, or where you want to go, or what you want to achieve, in our limited life-span. How to solve this dilemma?
As I discussed in a previous post, I always hold on to the view that this is the age of the responsible student. The progress of a practitioner of the internal art has to, ultimately, fall upon the practitioner himself. In particular for practices like meditation according to classic Taoists or Tibetan Buddhists which will take a practitioner years to perfect his skills to a...reasonably intermediate or advanced stage, if it can be achieved at all!
This leads me to a piece of very interesting saying in Taoist meditation/Neidan: 傳藥不傳火 (the master will only teach you the ingredients but not the way of fire [in modern terminology: energy management]). Many people interpreted the saying as: the teacher will withhold the final secret to himself, but some, like master Nan HuaiYin 南怀瑾, hold different opinion; and I share with Nan's view (again, it is an experiential sharing of view rather than an "academic" sharing of view here).
According to Nan (whose view I share), in his Can TongQi commentary, our human bodies are different. How much fire and where fire is needed and to what extent (such as how long), and when to stop, as well as the stopping sequence should not be the same for each person. In additional, logically speaking, a single person is impossible to experience all (or many) possible scenario of usage of fire. As a side-comment, this is the reason why many great tai-chi or other internal martial art masters were said to have weak physiques when they were young. Being weak, they had to try different and many ways in energy management, and that helped them to become great masters as they were!
Nan used cooking as an example. The master can teach you the ingredients and the way of cooking only, ultimately a student has to do the "firing" himself. In addition, in meditation, "firing" is done inside one's body, unable to be under the watchful eyes of his teacher (fair to say, a better teacher can still "interpret", to a certain extend, some internal happenings of his students through observing subtle changes on the outside).
Back to the main subject. So what should be the strategy of a "responsible student", for the dual objectives of progress and safety? This is my view:
1. He should be alerted at all times that he can feel (or feel that he can manage) the chi-generation process and its distribution routes.
2. When he detects anything wrong, he should try to manage it (by himself or with the help of his teacher) before proceeding further.
3. Technique-wise, he should learn the technique of how to direct the chi at outer stations (e.g. the heart chakra) back to the base chakra during the ending session. Oftentimes it is fine if some residual chi is still present in the body after the ending session, as long as it is under the mindful control of a practitioner.