Only having subject knowledge won’t make you a good teacher.
You need Empathy to know what your student is going through.
You need Mindfulness to be aware of your anger when a student is being unpleasant.
You need patience and care to teach a kid who is not getting you.
You need to tell stories to break down a complex, boring subject into something simple and fun!
Most importantly, you need love for the mission that you have undertaken.