What is the significance of the Gita’s definition of yoga as equanimity?

From: Devdatt

Lord says in Gita “Yogaha Samatvam Uchyate” equanimity is Yoga. This word “Sama” comes many times in Gita.

My questions are listed below:

1. What is the significance of this word.

2. Why this word Samam is repeated in almost every chapter of Gita.

3.In 5th Chapter it says Panditah Sama darishanh. How to cultivate this equal vision

4. Does this refer to becoming neutal 5, Why becoming neutral is recommended by Lord so much in Gita rather than cultivating spiritual emotion?