What causes mental instability?
The tyranny of negative self talk in ones mind when there is no positive outlet.
When we focus on those negative thoughts, in spite of all alternatives.
We need to realize the negative if we plan on to changing it to positive. The nine of swords is that realization of the primitive forces that must be raised. We must see the harshness and heartlessness in order to strive for higher ideals. We tend to fantasize that everything we do is good. The nine of swords is encouraging us to realize all consequences to our actions. Be prepared for the worst. Before the worst occurs and it wont be so bad.
We ultimately need to wake up from the nightmare of self doubt, by loving oneself in spite of all pervasive negativity.
That is all for now.
Peace & Calm