'Calmness of mind is one of the beautiful jewels of wisdom. It is the result of long and patient effort in self-control. Its presence is an indication of ripened experience, and of a more than ordinary knowledge of the laws and operations of thought.
As you can see the clear reflection, only when the water is still and calm, similarly only in a calm mind the clarity of thoughts prevails.
There is a big confusion in the world that 'Sererity' is only required for spiritual people / world. But the power of sererity and calmness is absolutely true and applicable in all field, weather you are a business man, a teacher or doing any other job.
No student want a teacher, who is always irritated. No one like to do business with a short tempered man.