The Bhagavad Gita (13.9) extols evenness of mind as a sign of spiritual knowledge. Evenness of mind is a sterling spiritual quality that helps us to acquire inner balance, a strong and mature character, concentration of mind, the capacity to make right decisions, and the ability to remain unfazed amid the uncertainties and dualities of life.
The undisciplined mind is compared to a restless monkey that is drunk with wine, then stung by a scorpion, and finally possessed by a demon. The mind swings to extremes of moods: happiness to misery, clarity to confusion, calmness to agitation. We experience these alternating moods because we remain identified with our mind. But Vedanta teaches that we are essentially divine and different from our mind and body. Evenness means an inner balance that keeps us undisturbed by changes in the mind.
Our thoughts and actions leave impressions in our mind, and they define our character. These impressions explain why different people face the same situation in different ways. As long as the mind remains undisciplined, our re-actions will be impulsive, immature, and dictated by external events and our attachments and aversions.
Evenness of mind implies a mature character born of a strong and one-pointed will. When we develop a strong and mature character, we become dispassionate, and our actions are measured and deliberate. For example, we will not be rude to others even when they are rude to us; we will not reject a good idea because we do not like its source.
An untrained mind is by nature attached to the senses and their objects. Such a mind dissipates a person's energy and makes concentration on anything difficult. Swami Vivekananda describes our predicament: "Free! We who cannot for a moment govern our own minds, nay, cannot hold our minds on a subject, focus it on a point to the exclusion of everything else for a moment! Yet we call ourselves free. Think of it! We cannot do as we know we ought to do even for a very short space of time. Some sense-desire will crop up, and immediately we obey it. Our conscience smites us for such weakness, but again and again we do it, we are always doing it. We cannot live up to a high standard of life, try as we will."
Swami Vivekananda says that concentration of mind is the core of education and the sole means to attain knowledge: "If I had to do my education over again, and had any voice in the matter, I would not study facts at all. I would develop the power of concentration and detachment, and then with a perfect instrument I could collect facts at will." This "perfect instrument" is developed by evenness of mind. Evenness prevents the mind from being swayed by emotions and helps us remain focused at all times. The Bhagavad Gita says, "This evenness is called yoga." (2.48)
A vacillating mind is habitually indecisive. It weakens us and clouds our perception. Far from helping us to solve problems, such a mind gets flustered in the face of problems and robs us of any initiative. Problems only get complicated if we do not face them boldly. With evenness of mind we can see a problem in its true perspective, analyze possible solutions, decide on the proper course of action, and follow it undeterred by any obstacle.