Often times one makes errors or losses due to their own acts. This may end up with them injuring or harming their children or their possessions. In this scenario one may lament but in reality it is their fault and hence others may not have as much sympathy or intervene. If that injury or harm was done to a third party then others can intervene and try to salvage the situation. Our ancestors formulated this proverb to warn others to not intervene where one is causing harm to their own possession.
The proverb is used to warn that in the event that one has caused injury or harm to their children or possessions, others must not intervene. It is also used to chide someone who intervened in a scenario like the one above