Behind Closed Doors (闭关) [Bi Guan] –
Martial artists who want to practise their martial skills in seclusion often do this. There are some reasons, the common ones being:
They do not want anyone else to steal the techniques that they are practising, or
The martial skills that they are practising has reached a critical juncture, and they cannot be disturbed while they are practising it. Should they be disturbed while in the midst of practising, the consequences are either their own death or sustaining serious injuries due to loss of energy control, or submitting to the Heart Devil and entering into a berserk mental state, attacking anything near them, while that will eventually end in their death or sustaining serious injuries.