"Letting the Cobra out" is an analogy referring to knowing when to leave someone else alone.
As defined by the Smithsonian, ". Despite its aggressive reputation, the king cobra is actually much more cautious than many smaller snakes. The cobra only attacks people when it is cornered, in self-defense or to protect its eggs."
When we corner a Cobra and see it's defensive position, we can't point the finger and say the Cobra is "bad", or "aggressive". We have to realize it is us who have cornered it causing this behavior. Likewise, if a Cobra is tending to its nest, we have to respect that approaching its line of defense could be met with grave consequences.
In domestic lives of humans, we have to respect each other's space, know when to leave each other alone, and if someone is trying to get out, don't block the exit! Just "let the Cobra out."
"My husband seems unkind and aggressive lately, but I know it is me that has cornered him, so I let the Cobra out."