The nature of a Yogi’s mind is further described in the next verse using a beautiful example.
यथा दीपो निवातस्थो नेङ्गते सोपमा स्मृता ।
योगिनो यतचित्तस्य युञ्जतो योगमात्मनः ॥६- १९॥
yathaa diipo nivaatastho neN^gate sopamaa smR^itaa .
yogino yatachittasya yuJNjato yogamaatmanaH .. 6.19..
The mind of the yogi practicing meditation on God is so disciplined and unwavering, like a light which does not flicker in a windless place.
yadaa – as : diipaH – light : nivaatasthaH – kept in a windless place : na – not : inN^gate – flickers : saa – this : upamaa – comparison : smR^itaa - is considered ( to be) : yoginaH - of the yogi : yatachittasya – of the disciplined mind : yuJNjataH – of him who is practising : yogaM - meditation : aatmanaH – on God :
The yogi’s mind is disciplined because he understands the true nature of worldly objects. He knows that desire and yearning for such objects is only like pouring ghee into fire because there can be no satisfaction at all from them. If you have one car, you want another car, if you have one house, you want another house, If you have one telephone, you want another telephone. It is said, “If you have one telephone, then it is a utility”. If you have two then it is a luxury. If you have three it is a show of wealth. If you have none, it is paradise!! Since the yogi’s mind is free from such yearnings and desires, he does not want anything other than God realization. He is hence able to keep his mind steady in his goal, just as the flame which is sheltered is able to remain steady.
In this verse, the yogi’s mind is described to be very steady. It is described to be like a flame that is sheltered. We might think, when some one is describing the steadiness, will it not be more appropriate to 
compare it to something steady and firm like a wall or a pillar or a mountain? How come, it has been compared to a flame? The example used here is most appropriate because, it takes into account the nature of the mind. The mind is flickering by nature and not steady at all times. Only under the right circumstances, the mind can be steadied. The wind described here is comparable to the various worldly objects that are present everywhere, just like wind which is present everywhere. When wind blows, then the flame flickers, similarly, when all these objects attract us, then, the mind wanders towards all of them and is disturbed by them. Just as there is light in the flame, there is the light of God in our minds. The light will be steady when the lamp is kept in a place that is sheltered from the winds. Similarly, when the mind is disciplined and sheltered by meditation, then there are no desires in the mind and it remains steady in the thoughts of God
