Emotions are simply thought processes like imagination, pain, or speech and controlling any of them is as simple as controlling your breathing (A so called involuntarily function like the rest of them). BTW, controlling your pulse and dreams work the same way also. It just takes practice and discipline.
Emotion and passion are two powerful entities that affect the outcome of an argument. Is it possible to ensure that emotion does not influence your critical thinking? If yes, how? If no, why not?
What a fascinating question.
There are situations where emotion and passion need to be "tamed" in order for critical thinking to be effective. This is true of situations where a lot is at stake, and passion or emotion risks 'over-riding' performance optimization through critical thinking.
For example, a soccer player scoring a decisive penalty. Or a surgeon saving someones lives.
Because of the high-passion/emotion nature of these scenarios, those that can drown out that aspect are afforded more critical thinking resources in their brain and tend to perform better.