This Chinese calligraphy tutorial explains next general rule of writing in cursive script (草書). The rule #5 says that the total number of stroke can be significantly reduced. Navigate to the "learning" section on this website, to view other calligraphy tutorials.
The principle of writing in cursive script is not necessarily to write fast, and by writing fast I am referring to quick brush strokes. Cursive script may often look as if it was written in hasted manner, but the truth is, that any calligraphy script requires precision.
If you write too quick, without having a required level of skill, the brush strokes will lack power and the so called "moving spirit" (行気). I will write a separate article on this, so for now it is enough to say that calligraphy beauty and strength is based on the energy flow throughout the single brush strokes, then the characters, and lastly the whole composition. This is the key to writing good calligraphy.
If you care to watch another video of mine where I copy a classic by Tang Dynasty (唐朝, 618 - 907 C.E.) calligrapher Sun Guoting (孫過庭, 646 - 691), you will notice that the brush moves with precision, and does not rush through the paper. On the other hand, it does not mean that one has to always write slowly. The rhythm and maintaining the balance between the skill and emotions is the key.
Going back to reducing the number of strokes while writing a calligraphy in cursive script, it is crucial to remember that every single character has a given form in cursive script (can be many of them), and those forms are not random. They are all based on the logic of stroke order in other scripts of Chinese calligraphy, the natural flow of writing, personal handwriting style, nature of the text, emotional state of the calligrapher, previous and following characters, and so on and so forth. In short, this and any other rules of cursive script ought to be studied in conjunction with the studies of other calligraphy scripts, and based on a solid knowledge of those.
Ponte Ryuurui (品天龍涙)