Chinese traditional culture identifies seven types of circumstances in which one should not play the Gu-qin:
When there is a high wind or heavy rain; When in a mood of great sorrow; When one's dress is untidy; When drunk and crazy; When one has not burned incense; When one does not understand music or is in rude surroundings; When one has not bathed or the place is dirty.
See also
Six Avoidances (Chinese Music)
References
The Seven Should-not-plays in playing Gu-qin are recorded in "Jing Shi Tong Yan", an ancient Chinese collection of novels written by Feng Meng-long (Feng Menglong) of the Ming Dynasty. The topic is also addressed in a Chinese classical literature masterpiece "Feng Shen Bang" (Gods of Honor).