An emotion is overcome only by a stronger contrary emotion
Formal Statement
An emotion can only be controlled or destroyed by another emotion contrary thereto, and with more power for controlling emotion.
In Plain Language
You cannot reason your way out of fear by pure logic alone — you need a counter-affect that is stronger than the fear. This is why Spinoza is not a naive rationalist. Knowing the truth is necessary but not sufficient; the truth must become an affect, a lived emotional force, to do any work. A philosophical insight that stays abstract cannot overpower the vivid pull of jealousy or anxiety. Practical freedom requires that understanding generate its own emotions — and as we saw, adequate ideas do generate joy.
Why This Follows
Step 12 (df-12) defined bondage as being moved by the strongest present affect. This step gives the law governing all affect change: only a stronger contrary affect can displace an existing one. This explains both why bondage is so persistent (bad affects are vivid and present) and what the remedy must look like (understanding must become affectively powerful).
Practical freedom must work through affects, not around them.
Connected Concepts
Can you think of a time when merely knowing something was irrational did not stop you from feeling it? What finally changed the feeling — if anything did?