BaZi: 病方 Sickness and Remedy of a chart.

A very old poem 五言独步WuYanDuBu - literally five words invincible steps begins with a famous phrase:

有病方为贵，无伤不是奇。格中如去病,   财禄喜相随. 
With sickness and remedy as noble, without injury it is not wonderful. If the structure has the sickness removed, wealth and fortune love to follow.

Seems like a simple yet astoundingly deep phrase.

'Sickness' refers to sickness in a chart. A lot of things can be sickness, for example

1. Hurting Officer meeting Officer,
2. Wealth being Robbed,
3. Seal being broken,
4. Officer mixed with Devil,
5. Food being seized
6. Repeating Officer
7. Officer being clashed
8. 7K structure with a weak DM

'Remedy' refers to the presence of an entity that rescues the structure, for example

1. Hurting Officer seeing Officer, Seal is the remedy
2. Wealth being Robbed, Officer or output can be the remedy
3. Seal being broken, parallel and Rob Wealth are the remedies
4. Officer mixed with Devil, the god that combines the Devil can be the remedy
5. Food being seized, Wealth as the remedy
6. Repeating Officer, combining away one officer is the remedy
7. Officer being clashed - the EB that combines with the clashing entity is the remedy.
8. 7K structure with a weak DM, Seal is the remedy

Remedy is the same concept as Minister God of ZPZQ. 

The concept of 'sickness and remedy' is emphasized by Master Zhang Nan, the author of SFTK and is also adapted by Master Xu LeWu in his commentary of ZPZQ.

Master Xu said:

病药。
Sickness and cure.

以扶为喜，则以伤其扶者为病；
With support as favorable, the entity that injure the support as sickness

以抑为喜，则以去其抑者为病。
With suppress as favorable, the entity that remove the suppression as sickness

除其病神，即谓之药。
The entity that removes the sickness god is called the cure (medicine)

此以病药取用神也。
This is how the Useful God is derived based on the concept of sickness and cure.

In summary, when a chart has a sickness, it needs a remedy. If both are present in the natal chart, we say the structure is complete 格成, denotes success. Otherwise, it is considered a broken structure, a structure that is incomplete. In this case, the subject needs to wait for the arrival of the remedy at the DaYun LP, AP or Small Luck Cycle.