(It is for) the practice of Samadhi and minimising the pain-bearing obstructions.
In plain words: Kriya Yoga is practiced to prepare for deep meditation and to weaken the troubles in us that cause pain. The teacher says it trains a mind that acts like a spoiled child.
Most of us make our minds like spoilt children, allowing them to do whatever they want. Therefore it is necessary that Kriya-yoga should be constantly practised, in order to gain control of the mind, and bring it into subjection. The obstructions to Yoga arise from lack of control, and cause us pain. They can only be removed by denying the mind, and holding it in check, through the means of Kriya-yoga.
Namaste.
A calm guide to life, the mind and the old teachings.